From 7fa904d855a215e216850285553d70fbd8fd5492 Mon Sep 17 00:00:00 2001
From: zenghongyi <277382367@qq.com>
Date: Tue, 22 Mar 2022 20:41:34 +0800
Subject: [PATCH 01/10] =?UTF-8?q?java=20=E5=BC=82=E5=B8=B8=E5=A4=84?=
 =?UTF-8?q?=E7=90=86?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 javase/pom.xml                                | 24 +++++++++++++
 .../src/main/java/com/hongyi/day1/Test01.java | 12 +++++++
 .../src/main/java/com/hongyi/day1/Test02.java | 34 +++++++++++++++++++
 .../src/test/java/com/hongyi/day1/Test01.java | 15 ++++++++
 4 files changed, 85 insertions(+)
 create mode 100644 javase/pom.xml
 create mode 100644 javase/src/main/java/com/hongyi/day1/Test01.java
 create mode 100644 javase/src/main/java/com/hongyi/day1/Test02.java
 create mode 100644 javase/src/test/java/com/hongyi/day1/Test01.java

diff --git a/javase/pom.xml b/javase/pom.xml
new file mode 100644
index 0000000..7e12f3c
--- /dev/null
+++ b/javase/pom.xml
@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>com.hongyi</groupId>
+    <artifactId>javase</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <properties>
+        <maven.compiler.source>11</maven.compiler.source>
+        <maven.compiler.target>11</maven.compiler.target>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>4.13.2</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+</project>
\ No newline at end of file
diff --git a/javase/src/main/java/com/hongyi/day1/Test01.java b/javase/src/main/java/com/hongyi/day1/Test01.java
new file mode 100644
index 0000000..d27ffe9
--- /dev/null
+++ b/javase/src/main/java/com/hongyi/day1/Test01.java
@@ -0,0 +1,12 @@
+package com.hongyi.day1;
+
+/**
+ * @Author Kisugi Takumi
+ * @Date 2022/3/22 17:06
+ * @Version 1.0
+ */
+public class Test01 {
+    public static void main(String[] args) {
+        Integer[] arr = new Integer[1024*1024*1024];
+    }
+}
diff --git a/javase/src/main/java/com/hongyi/day1/Test02.java b/javase/src/main/java/com/hongyi/day1/Test02.java
new file mode 100644
index 0000000..b1ca563
--- /dev/null
+++ b/javase/src/main/java/com/hongyi/day1/Test02.java
@@ -0,0 +1,34 @@
+package com.hongyi.day1;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+
+/**
+ * @Author Kisugi Takumi
+ * @Date 2022/3/22 20:07
+ * @Version 1.0
+ */
+public class Test02 {
+    public static void main(String[] args) {
+        FileInputStream fis = null;
+        try{
+            File file = new File("hello.txt");
+            fis = new FileInputStream(file);
+            int data = fis.read();
+            while (data != -1) {
+                System.out.println((char) data);
+                data = fis.read();
+            }
+        } catch (IOException e) {
+            e.printStackTrace();
+        } finally {
+            try {
+                fis.close();
+            } catch (IOException e) {
+                e.printStackTrace();
+            }
+        }
+    }
+}
diff --git a/javase/src/test/java/com/hongyi/day1/Test01.java b/javase/src/test/java/com/hongyi/day1/Test01.java
new file mode 100644
index 0000000..e784e5d
--- /dev/null
+++ b/javase/src/test/java/com/hongyi/day1/Test01.java
@@ -0,0 +1,15 @@
+package com.hongyi.day1;
+
+import org.junit.Test;
+
+/**
+ * @Author Kisugi Takumi
+ * @Date 2022/3/22 20:01
+ * @Version 1.0
+ */
+public class Test01 {
+    @Test
+    public void test1(){
+        System.out.println();
+    }
+}
-- 
Gitee


From efbc0de732f307b37d2ec99cc3ba41eaa9ae2d99 Mon Sep 17 00:00:00 2001
From: zenghongyi <277382367@qq.com>
Date: Wed, 23 Mar 2022 14:47:09 +0800
Subject: [PATCH 02/10] =?UTF-8?q?java=E5=9F=BA=E7=A1=80=20=E5=BC=82?=
 =?UTF-8?q?=E5=B8=B8?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../java/com/hongyi/day2/MyException.java     | 23 +++++++++
 .../com/hongyi/day2/ReturnExceptionDemo.java  | 33 ++++++++++++
 .../java/com/hongyi/day2/StudentTest.java     | 39 ++++++++++++++
 .../src/main/java/com/hongyi/day2/Test01.java | 51 +++++++++++++++++++
 .../src/main/java/com/hongyi/day2/Test02.java | 28 ++++++++++
 5 files changed, 174 insertions(+)
 create mode 100644 javase/src/main/java/com/hongyi/day2/MyException.java
 create mode 100644 javase/src/main/java/com/hongyi/day2/ReturnExceptionDemo.java
 create mode 100644 javase/src/main/java/com/hongyi/day2/StudentTest.java
 create mode 100644 javase/src/main/java/com/hongyi/day2/Test01.java
 create mode 100644 javase/src/main/java/com/hongyi/day2/Test02.java

diff --git a/javase/src/main/java/com/hongyi/day2/MyException.java b/javase/src/main/java/com/hongyi/day2/MyException.java
new file mode 100644
index 0000000..8d29ad0
--- /dev/null
+++ b/javase/src/main/java/com/hongyi/day2/MyException.java
@@ -0,0 +1,23 @@
+package com.hongyi.day2;
+
+/**
+ * @Author Kisugi Takumi
+ * @Date 2022/3/23 14:26
+ * @Version 1.0
+ */
+
+// 1.继承现有的异常体系结构RuntimeException、Exception
+public class MyException extends RuntimeException{
+
+    // 2.提供全局常量serialVersionUID
+    static final long serialVersionUID = -7034897190745766939L;
+
+    // 3.重载的构造器
+    public MyException() {
+
+    }
+
+    public MyException(String msg) {
+        super(msg);
+    }
+}
diff --git a/javase/src/main/java/com/hongyi/day2/ReturnExceptionDemo.java b/javase/src/main/java/com/hongyi/day2/ReturnExceptionDemo.java
new file mode 100644
index 0000000..13c4e9f
--- /dev/null
+++ b/javase/src/main/java/com/hongyi/day2/ReturnExceptionDemo.java
@@ -0,0 +1,33 @@
+package com.hongyi.day2;
+
+/**
+ * @Author Kisugi Takumi
+ * @Date 2022/3/23 14:34
+ * @Version 1.0
+ */
+public class ReturnExceptionDemo {
+    static void methodA() {
+        try {
+            System.out.println("进入方法A");
+            throw new RuntimeException("制造异常");
+        }finally {
+            System.out.println("用A方法的finally");
+        }
+    }
+    static void methodB() {
+        try {
+            System.out.println("进入方法B");
+            return;
+        } finally {
+            System.out.println("调用B方法的finally");
+        }
+    }
+    public static void main(String[] args) {
+        try {
+            methodA();
+        } catch (Exception e) {
+            System.out.println(e.getMessage());
+        }
+        methodB();
+    }
+}
diff --git a/javase/src/main/java/com/hongyi/day2/StudentTest.java b/javase/src/main/java/com/hongyi/day2/StudentTest.java
new file mode 100644
index 0000000..5150a43
--- /dev/null
+++ b/javase/src/main/java/com/hongyi/day2/StudentTest.java
@@ -0,0 +1,39 @@
+package com.hongyi.day2;
+
+/**
+ * @Author Kisugi Takumi
+ * @Date 2022/3/23 14:16
+ * @Version 1.0
+ */
+public class StudentTest {
+    public static void main(String[] args) {
+        try {
+            Student s = new Student();
+            s.registry(-1);
+            System.out.println(s);
+        } catch (Exception e) {
+            // e.printStackTrace();
+            System.out.println(e.getMessage());
+        }
+    }
+}
+
+class Student {
+    private int id;
+    public void registry(int id) {
+        if (id > 0) {
+            this.id = id;
+        } else {
+            // System.out.println("Error!");
+            // 手动抛出异常
+            throw new MyException("输入数据非法");
+        }
+    }
+
+    @Override
+    public String toString() {
+        return "Student{" +
+                "id=" + id +
+                '}';
+    }
+}
diff --git a/javase/src/main/java/com/hongyi/day2/Test01.java b/javase/src/main/java/com/hongyi/day2/Test01.java
new file mode 100644
index 0000000..ab090c7
--- /dev/null
+++ b/javase/src/main/java/com/hongyi/day2/Test01.java
@@ -0,0 +1,51 @@
+package com.hongyi.day2;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+
+/**
+ * @Author Kisugi Takumi
+ * @Date 2022/3/23 13:50
+ * @Version 1.0
+ */
+public class Test01 {
+    // main调用m2，捕获异常并处理
+    // main调用m3，因为m3已做了异常捕获和处理，因此不做异常处理
+    public static void main(String[] args) {
+        try {
+            m2();
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+        m3();
+    }
+
+    // m3调用m1，做捕获异常并异常处理
+    public static void m3() {
+        try {
+            m1();
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+
+    // m2调用m1，也将异常抛出，但不做异常处理
+    public static void m2() throws IOException {
+        m1();
+    }
+
+    // m1将异常抛出给调用者，不做异常处理
+    public static void m1() throws IOException {
+        File file = new File("hello.txt");
+        FileInputStream fis = new FileInputStream(file);
+        int data = fis.read();
+        while (data != -1) {
+            System.out.println((char) data);
+            data = fis.read();
+        }
+        fis.read();
+        System.out.println("Hello World");
+    }
+}
diff --git a/javase/src/main/java/com/hongyi/day2/Test02.java b/javase/src/main/java/com/hongyi/day2/Test02.java
new file mode 100644
index 0000000..7005787
--- /dev/null
+++ b/javase/src/main/java/com/hongyi/day2/Test02.java
@@ -0,0 +1,28 @@
+package com.hongyi.day2;
+
+import java.io.FileNotFoundException;
+import java.io.IOException;
+
+/**
+ * @Author Kisugi Takumi
+ * @Date 2022/3/23 14:02
+ * @Version 1.0
+ */
+public class Test02 {
+
+}
+
+class SuperClass {
+    public void method() throws IOException{
+
+    }
+}
+
+class SubClass1 extends SuperClass{
+    public void method() throws FileNotFoundException {
+
+    }
+}
+
+class SubClass2 extends SuperClass{
+}
-- 
Gitee


From 3c8f3021e9d3345aa83ba012337a82af00409cc6 Mon Sep 17 00:00:00 2001
From: zenghongyi <277382367@qq.com>
Date: Wed, 23 Mar 2022 15:49:21 +0800
Subject: [PATCH 03/10] =?UTF-8?q?java=20=E5=B8=B8=E7=94=A8=E7=B1=BB-?=
 =?UTF-8?q?=E5=AD=97=E7=AC=A6=E4=B8=B2?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../main/java/com/hongyi/day2/StringTest.java | 42 +++++++++++++++++++
 1 file changed, 42 insertions(+)
 create mode 100644 javase/src/main/java/com/hongyi/day2/StringTest.java

diff --git a/javase/src/main/java/com/hongyi/day2/StringTest.java b/javase/src/main/java/com/hongyi/day2/StringTest.java
new file mode 100644
index 0000000..f012a6f
--- /dev/null
+++ b/javase/src/main/java/com/hongyi/day2/StringTest.java
@@ -0,0 +1,42 @@
+package com.hongyi.day2;
+
+/**
+ * @Author Kisugi Takumi
+ * @Date 2022/3/23 14:52
+ * @Version 1.0
+ */
+public class StringTest {
+    public static void main(String[] args) {
+        test2();
+    }
+
+    static void test1() {
+        String s1 = "abc"; // 字面量的定义方式
+        String s2 = "abc";
+
+        System.out.println(s1 == s2); // 比较s1和s2的地址值
+
+        s1 = "hello";
+        System.out.println(s1);
+        System.out.println(s2);
+
+    }
+
+    static void test2() {
+        // 此时s1和s2地址对应的数据都在字符串常量池中
+        String s1 = "abc";
+        String s2 = "abc";
+
+        // 此时s3和s4地址对应的数据都在堆空间中
+        String s3 = new String("abc");
+        String s4 = new String("abc");
+
+        System.out.println(s1 == s2); // true
+        System.out.println(s1 == s3); // false
+        System.out.println(s3 == s4); // false
+    }
+}
+
+class Person {
+
+}
-- 
Gitee


From 57ab8ea3c49568a6466d99572f8489250cad89a4 Mon Sep 17 00:00:00 2001
From: zenghongyi <277382367@qq.com>
Date: Fri, 25 Mar 2022 19:19:52 +0800
Subject: [PATCH 04/10] =?UTF-8?q?java=E9=AB=98=E7=BA=A7=20String=E5=B8=B8?=
 =?UTF-8?q?=E7=94=A8=E6=96=B9=E6=B3=95=E5=92=8C=E6=95=B0=E6=8D=AE=E8=BD=AC?=
 =?UTF-8?q?=E6=8D=A2?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../main/java/com/hongyi/day2/StringTest.java |   6 +-
 .../src/test/java/com/hongyi/day1/Test01.java |   6 +
 .../src/test/java/com/hongyi/day2/Test01.java | 117 ++++++++++++++++++
 .../src/test/java/com/hongyi/day2/Test02.java |  66 ++++++++++
 4 files changed, 192 insertions(+), 3 deletions(-)
 create mode 100644 javase/src/test/java/com/hongyi/day2/Test01.java
 create mode 100644 javase/src/test/java/com/hongyi/day2/Test02.java

diff --git a/javase/src/main/java/com/hongyi/day2/StringTest.java b/javase/src/main/java/com/hongyi/day2/StringTest.java
index f012a6f..8c2957f 100644
--- a/javase/src/main/java/com/hongyi/day2/StringTest.java
+++ b/javase/src/main/java/com/hongyi/day2/StringTest.java
@@ -7,7 +7,7 @@ package com.hongyi.day2;
  */
 public class StringTest {
     public static void main(String[] args) {
-        test2();
+        test3();
     }
 
     static void test1() {
@@ -35,8 +35,8 @@ public class StringTest {
         System.out.println(s1 == s3); // false
         System.out.println(s3 == s4); // false
     }
-}
 
-class Person {
+    static void test3() {
 
+    }
 }
diff --git a/javase/src/test/java/com/hongyi/day1/Test01.java b/javase/src/test/java/com/hongyi/day1/Test01.java
index e784e5d..cfeb952 100644
--- a/javase/src/test/java/com/hongyi/day1/Test01.java
+++ b/javase/src/test/java/com/hongyi/day1/Test01.java
@@ -1,6 +1,7 @@
 package com.hongyi.day1;
 
 import org.junit.Test;
+import org.junit.runner.RunWith;
 
 /**
  * @Author Kisugi Takumi
@@ -12,4 +13,9 @@ public class Test01 {
     public void test1(){
         System.out.println();
     }
+
+    @Test
+    public void test2() {
+        System.out.println("Hello World");
+    }
 }
diff --git a/javase/src/test/java/com/hongyi/day2/Test01.java b/javase/src/test/java/com/hongyi/day2/Test01.java
new file mode 100644
index 0000000..61da1ef
--- /dev/null
+++ b/javase/src/test/java/com/hongyi/day2/Test01.java
@@ -0,0 +1,117 @@
+package com.hongyi.day2;
+
+import org.junit.Test;
+
+import java.util.Locale;
+
+/**
+ * @Author Kisugi Takumi
+ * @Date 2022/3/25 17:03
+ * @Version 1.0
+ */
+public class Test01 {
+    @Test
+    public void test0() {
+        String s1 = "javaEE";
+        String s2 = "hadoop";
+
+        String s3 = "javaEEhadoop";
+        String s4 = "javaEE" + "hadoop";
+        String s5 = s1 + "hadoop";
+        String s6 = "javaEE" + s2;
+        String s7 = s1 + s2;
+
+        System.out.println(s3 == s4); // true
+        System.out.println(s3 == s5); // false
+        System.out.println(s3 == s6); // false
+        System.out.println(s3 == s7); // false
+        System.out.println(s5 == s6); // false
+        System.out.println(s5 == s7); // false
+        System.out.println(s6 == s7); // false
+
+        String s8 = s5.intern();
+        System.out.println(s3 == s8); // true
+    }
+
+    @Test
+    public void test1() {
+        String s1 = "HelloWorld";
+        System.out.println(s1.length()); // 10
+        System.out.println(s1.charAt(1)); // e
+        System.out.println(s1.isEmpty()); // false
+
+        String s2 = s1.toUpperCase(Locale.ROOT);
+        System.out.println(s1); // HelloWorld
+        System.out.println(s2); // HELLOWORLD
+
+        String s3 = "  hello world     ";
+        String s4 = s3.trim();
+        System.out.println(s3); // 不变
+        System.out.println(s4); // hello world
+    }
+
+    @Test
+    public void test2() {
+        String s1 = "abc";
+        String s2 = "def";
+        String s3 = s1.concat(s2);
+        System.out.println(s3); // abcdef
+
+        String s4 = "abc";
+        String s5 = new String("abz");
+        String s6 = "abc";
+        System.out.println(s4.compareTo(s5)); // -23
+        System.out.println(s4.compareTo(s6)); // 0
+
+        String s7 = "Hongyi";
+        String s8 = s7.substring(1);
+        String s9 = s7.substring(1,3);
+        System.out.println(s8); // ongyi
+        System.out.println(s9); // on
+    }
+
+    @Test
+    public void test3() {
+        String s1 = "helloworld";
+        boolean b1 = s1.endsWith("rld");
+        boolean b2 = s1.startsWith("ll");
+        System.out.println(b1); // true
+        System.out.println(b2); // false
+
+        boolean b3 = s1.contains("llo");
+        System.out.println(b3); // true
+
+        int i1 = s1.indexOf("lo");
+        int i2 = s1.indexOf("m");
+        System.out.println(i1); // 3
+        System.out.println(i2); // -1
+    }
+
+    @Test
+    public void test4() {
+        String s1 = "helloworld";
+        String s2 = s1.replace("h", "a");
+        System.out.println(s1); // helloworld
+        System.out.println(s2); // aelloworld
+
+        String s3 = s1.replace("hello", "hongyi");
+        System.out.println(s3); // hongyiworld
+
+        String s4 = "12hello34world4";
+        // 把字符串中的数字替换成逗号 , 如果结果中开头和结尾有 , 的话则去掉
+        String s5 = s4.replaceAll("\\d+", ",").replaceAll("^,|,$", "");
+        System.out.println(s5); // hello,world
+    }
+
+    @Test
+    public void test5() {
+        String s1 = "hello|world|java";
+        String[] s2 = s1.split("\\|");
+        for (String s : s2) {
+            System.out.println(s);
+            // hello
+            // world
+            // java
+        }
+    }
+}
diff --git a/javase/src/test/java/com/hongyi/day2/Test02.java b/javase/src/test/java/com/hongyi/day2/Test02.java
new file mode 100644
index 0000000..cc5021b
--- /dev/null
+++ b/javase/src/test/java/com/hongyi/day2/Test02.java
@@ -0,0 +1,66 @@
+package com.hongyi.day2;
+
+import org.junit.Test;
+
+/**
+ * @Author Kisugi Takumi
+ * @Date 2022/3/25 18:53
+ * @Version 1.0
+ */
+public class Test02 {
+    @Test
+    public void test0() {
+        String s1 = "123";
+        int num = Integer.parseInt(s1);
+        System.out.println(num);
+
+        String s2 = "true";
+        boolean flag = Boolean.parseBoolean(s2);
+        System.out.println(s2);
+
+        String s3 = "123.123";
+        double num1 = Double.parseDouble(s3);
+        System.out.println(num1);
+    }
+
+    @Test
+    public void test1() {
+        int num = 123;
+        String s = String.valueOf(num);
+        System.out.println(s);
+    }
+    
+    @Test
+    public void test2() {
+        String s1 = "123abc";
+        char[] charArray = s1.toCharArray();
+        for (char c : charArray){
+            System.out.println(c);
+        }
+    }
+
+    @Test
+    public void test3() {
+        char[] arr = new char[]{'h', 'e', 'l', 'l', 'o'};
+        String s = new String(arr);
+        System.out.println(s);
+    }
+
+    @Test
+    public void test4() {
+        String s1 = "abc123";
+        byte[] bytes = s1.getBytes();
+        for(byte b:bytes) {
+            System.out.print(b + ","); // 97,98,99,49,50,51
+        }
+    }
+
+    @Test
+    public void test5() {
+        String s1 = "abc123";
+        byte[] bytes = s1.getBytes();
+        // 采用默认字符集解码
+        String s = new String(bytes);
+        System.out.println(s); // abc123
+    }
+}
-- 
Gitee


From 47716490f18f261476cf87b5942fabc52d537d42 Mon Sep 17 00:00:00 2001
From: zenghongyi <277382367@qq.com>
Date: Sat, 26 Mar 2022 16:33:45 +0800
Subject: [PATCH 05/10] =?UTF-8?q?java=E9=AB=98=E7=BA=A7=20StringBuffer=20S?=
 =?UTF-8?q?tringBuilder=20=E6=97=A5=E6=9C=9F=E5=92=8C=E6=97=B6=E9=97=B4?=
 =?UTF-8?q?=E7=9B=B8=E5=85=B3=E7=9A=84api?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../java/com/hongyi/day3/DateTimeTest.java    | 32 ++++++++
 .../hongyi/day3/StringBufferBuilderTest.java  | 77 +++++++++++++++++++
 2 files changed, 109 insertions(+)
 create mode 100644 javase/src/test/java/com/hongyi/day3/DateTimeTest.java
 create mode 100644 javase/src/test/java/com/hongyi/day3/StringBufferBuilderTest.java

diff --git a/javase/src/test/java/com/hongyi/day3/DateTimeTest.java b/javase/src/test/java/com/hongyi/day3/DateTimeTest.java
new file mode 100644
index 0000000..3d0a896
--- /dev/null
+++ b/javase/src/test/java/com/hongyi/day3/DateTimeTest.java
@@ -0,0 +1,32 @@
+package com.hongyi.day3;
+
+import org.junit.Test;
+
+import java.util.Date;
+
+/**
+ * @Author Kisugi Takumi
+ * @Date 2022/3/26 16:09
+ * @Version 1.0
+ */
+public class DateTimeTest {
+    @Test
+    public void test0() {
+        long time = System.currentTimeMillis();
+        System.out.println(time);
+    }
+
+    @Test
+    public void test1() {
+        Date date1 = new Date();
+        System.out.println(date1);
+        System.out.println(date1.getTime());
+
+        Date date2 = new Date(1648282572968L);
+        System.out.println(date2);
+
+        java.sql.Date date3 = new java.sql.Date(1648282572968L);
+        System.out.println(date3);
+
+    }
+}
diff --git a/javase/src/test/java/com/hongyi/day3/StringBufferBuilderTest.java b/javase/src/test/java/com/hongyi/day3/StringBufferBuilderTest.java
new file mode 100644
index 0000000..90d5043
--- /dev/null
+++ b/javase/src/test/java/com/hongyi/day3/StringBufferBuilderTest.java
@@ -0,0 +1,77 @@
+package com.hongyi.day3;
+
+import org.junit.Test;
+
+/**
+ * @Author Kisugi Takumi
+ * @Date 2022/3/26 15:23
+ * @Version 1.0
+ */
+public class StringBufferBuilderTest {
+    @Test
+    public void test0() {
+        StringBuffer sb1 = new StringBuffer("abc");
+        // 该方法没有返回值，修改的就是sb1本身的值
+        sb1.setCharAt(0, 'm');
+        System.out.println(sb1);
+    }
+
+    @Test
+    public void test1() {
+        StringBuffer s1 = new StringBuffer("abc");
+        s1.append('1');
+        s1.append(1);
+        System.out.println(s1); // abc11
+
+        s1.delete(0, 1);
+        System.out.println(s1); // bc11
+
+        s1.replace(0, 1, "ab");
+        System.out.println(s1); // abc11
+
+        System.out.println(s1.reverse()); // 11cba
+    }
+
+    @Test
+    public void test2() {
+        //初始设置
+        long startTime = 0L;
+        long endTime = 0L;
+        String text = "";
+        StringBuffer buffer = new StringBuffer("");
+        StringBuilder builder = new StringBuilder("");
+        //开始对比
+        startTime = System.currentTimeMillis();
+        for (int i = 0; i < 20000; i++) {
+            buffer.append(String.valueOf(i));
+        }
+        endTime = System.currentTimeMillis();
+        System.out.println("StringBuffer的执行时间：" + (endTime - startTime));
+        startTime = System.currentTimeMillis();
+        for (int i = 0; i < 20000; i++) {
+            builder.append(String.valueOf(i));
+        }
+        endTime = System.currentTimeMillis();
+        System.out.println("StringBuilder的执行时间：" + (endTime - startTime));
+        startTime = System.currentTimeMillis();
+        for (int i = 0; i < 20000; i++) {
+            text = text + i;
+        }
+        endTime = System.currentTimeMillis();
+        System.out.println("String的执行时间：" + (endTime - startTime));
+    }
+
+    @Test
+    public void test3() {
+        String str = null;
+        StringBuffer sb = new StringBuffer();
+        sb.append(str);
+
+        System.out.println(sb.length()); // 4
+        System.out.println(sb); // "null"
+
+        StringBuffer sb1 = new StringBuffer(str);
+        System.out.println(sb1); // 报错java.lang.NullPointerException
+    }
+
+}
-- 
Gitee


From b3b3d09e8e4b0ee3ba4244da6c82ac9d441f98d1 Mon Sep 17 00:00:00 2001
From: zenghongyi <277382367@qq.com>
Date: Mon, 28 Mar 2022 15:09:19 +0800
Subject: [PATCH 06/10] =?UTF-8?q?java=E9=AB=98=E7=BA=A7=20=E6=97=A5?=
 =?UTF-8?q?=E6=9C=9F=E6=97=B6=E9=97=B4=E7=9B=B8=E5=85=B3=E7=9A=84api?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../java/com/hongyi/day3/DateTimeTest.java    | 102 ++++++++++++++++++
 .../hongyi/day3/StringBufferBuilderTest.java  |   4 +-
 2 files changed, 104 insertions(+), 2 deletions(-)

diff --git a/javase/src/test/java/com/hongyi/day3/DateTimeTest.java b/javase/src/test/java/com/hongyi/day3/DateTimeTest.java
index 3d0a896..d4dc022 100644
--- a/javase/src/test/java/com/hongyi/day3/DateTimeTest.java
+++ b/javase/src/test/java/com/hongyi/day3/DateTimeTest.java
@@ -2,6 +2,12 @@ package com.hongyi.day3;
 
 import org.junit.Test;
 
+import java.text.ParseException;
+import java.text.SimpleDateFormat;
+import java.time.*;
+import java.time.format.DateTimeFormatter;
+import java.time.format.FormatStyle;
+import java.time.temporal.TemporalAccessor;
 import java.util.Date;
 
 /**
@@ -29,4 +35,100 @@ public class DateTimeTest {
         System.out.println(date3);
 
     }
+
+    @Test
+    public void test2() throws ParseException {
+        // 实例化SimpleDateFormat，使用默认的构造器
+        SimpleDateFormat sdf = new SimpleDateFormat();
+        // 格式化日期
+        Date date = new Date();
+        // System.out.println(date);
+        String format = sdf.format(date);
+        System.out.println(format); // 2022/3/28 下午2:11
+
+        // 解析
+        String str = "22/3/28 上午11:43";
+        Date date1 = sdf.parse(str);
+        System.out.println(date1); // Mon Mar 28 11:43:00 CST 2022
+
+        // ----------------------------
+        // 按照指定的方式格式化和解析
+        SimpleDateFormat sdf1 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
+        String format1 = sdf1.format(date);
+        System.out.println(format1); // 2022-03-28 14:18:45
+
+        // 解析：要求符合sdf识别的格式
+        Date date2 = sdf1.parse("2020-01-01 00:00:00");
+        System.out.println(date2); // Wed Jan 01 00:00:00 CST 2020
+    }
+
+    @Test
+    public void test3() {
+        // 获取当前日期、时间、日期+时间
+        LocalDate localDate = LocalDate.now();
+        LocalTime localTime = LocalTime.now();
+        LocalDateTime localDateTime = LocalDateTime.now();
+
+        System.out.println(localDate); // 2022-03-28
+        System.out.println(localTime); // 14:36:49.369528800
+        System.out.println(localDateTime); // 2022-03-28T14:36:49.369528800
+
+        // of()
+        // 设置指定的年、月、日、时、分、秒，没有偏移量
+        LocalDateTime localDateTime1 = LocalDateTime.of(2020, 10,6, 13, 23, 59);
+        System.out.println(localDateTime1); // 2020-10-06T13:23:59
+
+        //getXXX():
+        System.out.println(localDateTime.getDayOfMonth()); // 28
+        System.out.println(localDateTime.getDayOfWeek()); // MONDAY
+    }
+
+    @Test
+    public void test4() {
+        // 获取UTC时区（本初子午线）的Instant类的对象
+        Instant instant = Instant.now();
+        System.out.println(instant); // 2022-03-28T06:46:17.166469400Z
+
+        // 加8个小时
+        OffsetDateTime offsetDateTime = instant.atOffset(ZoneOffset.ofHours(8));
+        System.out.println(offsetDateTime); // 2022-03-28T14:49:04.847567700+08:00
+
+        // 获得时间戳
+        long milli = instant.toEpochMilli();
+        System.out.println(milli); // 1648450257945
+
+        // 通过时间戳创建Instant对象
+        Instant instant1 = Instant.ofEpochMilli(1648450257945L);
+        System.out.println(instant1);// 2022-03-28T06:50:57.945Z
+    }
+
+    @Test
+    public void test5() {
+        // 方式一：预定义的标准格式
+        DateTimeFormatter formatter = DateTimeFormatter.ISO_LOCAL_DATE_TIME;
+        // 格式化：日期 --> 字符串
+        LocalDateTime localDateTime = LocalDateTime.now();
+        String str1 = formatter.format(localDateTime);
+        System.out.println("格式化之前: " + localDateTime); // 2022-03-28T14:58:27.893263500
+        System.out.println("格式化之后: " + str1); // 2022-03-28T14:58:27.8932635
+
+        // 解析
+        TemporalAccessor parse = formatter.parse("2022-03-28T14:58:27.8932635");
+        System.out.println(parse); // {},ISO resolved to 2022-03-28T14:58:27.893263500
+
+        // 方式二：本地相关的格式
+        DateTimeFormatter formatter1 = DateTimeFormatter.ofLocalizedDateTime(FormatStyle.SHORT);
+        // 格式化
+        String str2 = formatter1.format(localDateTime);
+        System.out.println(str2); // 2022/3/28 下午3:01
+
+        // 方式三：自定义格式，重点
+        DateTimeFormatter formatter2 = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
+        // 格式化
+        String str3 = formatter2.format(localDateTime);
+        System.out.println(str3); // 2022-03-28 15:04:37
+        // 解析
+        TemporalAccessor parse1 = formatter2.parse("2021-01-01 13:00:01");
+        System.out.println(parse1); // {},ISO resolved to 2021-01-01T13:00:01
+    }
 }
diff --git a/javase/src/test/java/com/hongyi/day3/StringBufferBuilderTest.java b/javase/src/test/java/com/hongyi/day3/StringBufferBuilderTest.java
index 90d5043..027dee5 100644
--- a/javase/src/test/java/com/hongyi/day3/StringBufferBuilderTest.java
+++ b/javase/src/test/java/com/hongyi/day3/StringBufferBuilderTest.java
@@ -70,8 +70,8 @@ public class StringBufferBuilderTest {
         System.out.println(sb.length()); // 4
         System.out.println(sb); // "null"
 
-        StringBuffer sb1 = new StringBuffer(str);
-        System.out.println(sb1); // 报错java.lang.NullPointerException
+        StringBuffer sb1 = new StringBuffer(str); // 报错java.lang.NullPointerException
+        System.out.println(sb1);
     }
 
 }
-- 
Gitee


From 4c878a65f4230a150f4fd1a62b081e1306bd9735 Mon Sep 17 00:00:00 2001
From: zenghongyi <277382367@qq.com>
Date: Mon, 28 Mar 2022 20:01:06 +0800
Subject: [PATCH 07/10] =?UTF-8?q?java=E9=AB=98=E7=BA=A7=20=E6=AF=94?=
 =?UTF-8?q?=E8=BE=83=E5=99=A8=E5=92=8CSystem=E7=B1=BB?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 javase/pom.xml                                |  5 ++
 .../src/main/java/com/hongyi/day4/Goods.java  | 38 +++++++++
 .../java/com/hongyi/day4/CompareTest.java     | 83 +++++++++++++++++++
 .../test/java/com/hongyi/day4/SystemTest.java | 35 ++++++++
 4 files changed, 161 insertions(+)
 create mode 100644 javase/src/main/java/com/hongyi/day4/Goods.java
 create mode 100644 javase/src/test/java/com/hongyi/day4/CompareTest.java
 create mode 100644 javase/src/test/java/com/hongyi/day4/SystemTest.java

diff --git a/javase/pom.xml b/javase/pom.xml
index 7e12f3c..3265392 100644
--- a/javase/pom.xml
+++ b/javase/pom.xml
@@ -20,5 +20,10 @@
             <version>4.13.2</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <version>1.18.22</version>
+        </dependency>
     </dependencies>
 </project>
\ No newline at end of file
diff --git a/javase/src/main/java/com/hongyi/day4/Goods.java b/javase/src/main/java/com/hongyi/day4/Goods.java
new file mode 100644
index 0000000..f998f42
--- /dev/null
+++ b/javase/src/main/java/com/hongyi/day4/Goods.java
@@ -0,0 +1,38 @@
+package com.hongyi.day4;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.ToString;
+
+/**
+ * @Author Kisugi Takumi
+ * @Date 2022/3/28 19:15
+ * @Version 1.0
+ */
+@Data
+@AllArgsConstructor
+@ToString
+public class Goods implements Comparable{
+    private String name;
+    private double price;
+
+    // 先按照价格从低到高进行排序
+    // 再按照产品名称从高到低排序
+    @Override
+    public int compareTo(Object o) {
+        if (o instanceof Goods){
+            Goods goods = (Goods) o;
+            if(this.price > goods.price){
+                return 1;
+            }else if(this.price < goods.price){
+                return -1;
+            }else{
+                // return 0;
+                return -this.name.compareTo(goods.name);
+            }
+            // 方式二：
+            // return Double.compare(this.price, goods.price);
+        }
+        throw new RuntimeException("传入的数据类型不一致");
+    }
+}
diff --git a/javase/src/test/java/com/hongyi/day4/CompareTest.java b/javase/src/test/java/com/hongyi/day4/CompareTest.java
new file mode 100644
index 0000000..764e34a
--- /dev/null
+++ b/javase/src/test/java/com/hongyi/day4/CompareTest.java
@@ -0,0 +1,83 @@
+package com.hongyi.day4;
+
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.Comparator;
+
+/**
+ * @Author Kisugi Takumi
+ * @Date 2022/3/28 19:06
+ * @Version 1.0
+ */
+public class CompareTest {
+    @Test
+    public void test0() {
+        String[] arr = new String[]{"AA", "CC", "KK", "MM", "GG", "JJ", "DD"};
+        Arrays.sort(arr);
+        System.out.println(Arrays.toString(arr)); // [AA, CC, DD, GG, JJ, KK, MM]
+    }
+
+    @Test
+    public void test1() {
+        Goods[] goods = new Goods[5];
+        goods[0] = new Goods("lenovo", 34);
+        goods[1] = new Goods("dell", 43);
+        goods[2] = new Goods("xiaomi", 12);
+        goods[3] = new Goods("huawei", 65);
+        goods[4] = new Goods("microsoft", 43);
+
+        Arrays.sort(goods);
+        System.out.println(Arrays.toString(goods));
+        //[Goods(name=xiaomi, price=12.0),
+        // Goods(name=lenovo, price=34.0),
+        // Goods(name=microsoft, price=43.0),
+        // Goods(name=dell, price=43.0),
+        // Goods(name=huawei, price=65.0)]
+    }
+
+    @Test
+    public void test2(){
+        String[] arr = new String[]{"AA", "CC", "KK", "MM", "GG", "JJ", "DD"};
+        Arrays.sort(arr, new Comparator<String>() {
+            @Override
+            public int compare(String o1, String o2) {
+                // 从大到小排序
+                return -o1.compareTo(o2);
+            }
+        });
+        System.out.println(Arrays.toString(arr));
+        // [MM, KK, JJ, GG, DD, CC, AA]
+    }
+
+    @Test
+    public void test3(){
+        Goods[] goods = new Goods[6];
+        goods[0] = new Goods("lenovo", 34);
+        goods[1] = new Goods("dell", 43);
+        goods[2] = new Goods("xiaomi", 12);
+        goods[3] = new Goods("huawei", 65);
+        goods[4] = new Goods("microsoft", 43);
+        goods[5] = new Goods("microsoft", 12);
+
+        Arrays.sort(goods, new Comparator<Goods>() {
+            @Override
+            public int compare(Goods o1, Goods o2) {
+                // 先照产品名称从低到高排序
+                // 再按照价格从高到低进行排序
+                if (o1.getName().equals(o2.getName())){
+                    return -Double.compare(o1.getPrice(), o2.getPrice());
+                }else{
+                    return o1.getName().compareTo(o2.getName());
+                }
+            }
+        });
+        System.out.println(Arrays.toString(goods));
+        // [Goods(name=dell, price=43.0),
+        // Goods(name=huawei, price=65.0),
+        // Goods(name=lenovo, price=34.0),
+        // Goods(name=microsoft, price=43.0),
+        // Goods(name=microsoft, price=12.0),
+        // Goods(name=xiaomi, price=12.0)]
+    }
+}
diff --git a/javase/src/test/java/com/hongyi/day4/SystemTest.java b/javase/src/test/java/com/hongyi/day4/SystemTest.java
new file mode 100644
index 0000000..c993a76
--- /dev/null
+++ b/javase/src/test/java/com/hongyi/day4/SystemTest.java
@@ -0,0 +1,35 @@
+package com.hongyi.day4;
+
+import org.junit.Test;
+
+/**
+ * @Author Kisugi Takumi
+ * @Date 2022/3/28 19:56
+ * @Version 1.0
+ */
+public class SystemTest {
+    @Test
+    public void test0(){
+        String javaVersion = System.getProperty("java.version");
+        System.out.println("java的version:" + javaVersion);
+        String javaHome = System.getProperty("java.home");
+        System.out.println("java的home:" + javaHome);
+        String osName = System.getProperty("os.name");
+        System.out.println("os的name:" + osName);
+        String osVersion = System.getProperty("os.version");
+        System.out.println("os的version:" + osVersion);
+        String userName = System.getProperty("user.name");
+        System.out.println("user的name:" + userName);
+        String userHome = System.getProperty("user.home");
+        System.out.println("user的home:" + userHome);
+        String userDir = System.getProperty("user.dir");
+        System.out.println("user的dir:" + userDir);
+        // java的version:11.0.10
+        // java的home:C:\Users\Hongyi\.jdks\corretto-11.0.10
+        // os的name:Windows 10
+        // os的version:10.0
+        // user的name:Hongyi
+        // user的home:C:\Users\Hongyi
+        // user的dir:E:\develop\study\backend_study\javase
+    }
+}
-- 
Gitee


From 69813119b3802ac35c56a49fb481e54e903e3be7 Mon Sep 17 00:00:00 2001
From: zenghongyi <277382367@qq.com>
Date: Tue, 29 Mar 2022 19:22:10 +0800
Subject: [PATCH 08/10] =?UTF-8?q?java=E9=AB=98=E7=BA=A7=20=E6=9E=9A?=
 =?UTF-8?q?=E4=B8=BE=E7=B1=BB=E5=92=8C=E6=B3=A8=E8=A7=A3?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../java/com/hongyi/day4/AnnotationTest.java  |  59 ++++++++++
 .../test/java/com/hongyi/day4/EnumTest.java   | 105 ++++++++++++++++++
 2 files changed, 164 insertions(+)
 create mode 100644 javase/src/test/java/com/hongyi/day4/AnnotationTest.java
 create mode 100644 javase/src/test/java/com/hongyi/day4/EnumTest.java

diff --git a/javase/src/test/java/com/hongyi/day4/AnnotationTest.java b/javase/src/test/java/com/hongyi/day4/AnnotationTest.java
new file mode 100644
index 0000000..8f13744
--- /dev/null
+++ b/javase/src/test/java/com/hongyi/day4/AnnotationTest.java
@@ -0,0 +1,59 @@
+package com.hongyi.day4;
+
+import org.junit.Test;
+
+/**
+ * @Author Kisugi Takumi
+ * @Date 2022/3/29 19:04
+ * @Version 1.0
+ */
+public class AnnotationTest {
+    @Test
+    public void test0(){
+        Person p = new Person("Hongyi", 24);
+        p.eat();
+
+        @SuppressWarnings("unused")
+        int a = 10;
+    }
+}
+
+class Person{
+    private String name;
+    private int age;
+
+    public Person() {
+
+    }
+
+    public Person(String name, int age) {
+        this.name = name;
+        this.age = age;
+    }
+
+    public void walk(){
+        System.out.println("walk...");
+    }
+
+    @Deprecated
+    public void eat(){
+        System.out.println("eat...");
+    }
+
+}
+
+interface Infor{
+    void show();
+}
+
+class Student extends Person implements Infor{
+    @Override
+    public void walk() {
+        System.out.println("student walks...");
+    }
+
+    @Override
+    public void show() {
+        System.out.println("student shows...");
+    }
+}
\ No newline at end of file
diff --git a/javase/src/test/java/com/hongyi/day4/EnumTest.java b/javase/src/test/java/com/hongyi/day4/EnumTest.java
new file mode 100644
index 0000000..d2ae8dd
--- /dev/null
+++ b/javase/src/test/java/com/hongyi/day4/EnumTest.java
@@ -0,0 +1,105 @@
+package com.hongyi.day4;
+
+import org.junit.Test;
+
+/**
+ * @Author Kisugi Takumi
+ * @Date 2022/3/29 18:23
+ * @Version 1.0
+ */
+public class EnumTest {
+    @Test
+    public void test0(){
+        System.out.println(Season.SPRING); // SPRING
+        System.out.println(Season.class.getSuperclass()); // class java.lang.Enum
+    }
+
+    @Test
+    public void test1(){
+        Season summer = Season.SUMMER;
+        // 枚举类对象的toString方法
+        // 输出枚举类对象的名称
+        System.out.println(summer.toString()); // SUMMER
+        // values()返回枚举类型的对象数组
+        Season[] seasons = Season.values();
+        for(Season season:seasons){
+            System.out.println(season);
+            // SPRING
+            // SUMMER
+            // AUTUMN
+            // WINTER
+        }
+        Thread.State[] states = Thread.State.values();
+        for(Thread.State state:states){
+            System.out.println(state);
+            // NEW
+            // RUNNABLE
+            // BLOCKED
+            // WAITING
+            // TIMED_WAITING
+            // TERMINATED
+        }
+        //---------------------------------------------
+        Season winter = Season.valueOf("WINTER");
+        System.out.println(winter); // WINTER
+    }
+
+    @Test
+    public void test2(){
+        Season autumn = Season.AUTUMN;
+        autumn.show(); // 这是秋天
+    }
+}
+
+interface Info{
+    void show();
+}
+
+enum Season implements Info{
+    // 1.提供当前枚举类的对象
+    // 多个对象之间用 , 隔开，最后一个用 ;
+    SPRING("春天", "春暖花开"){
+        @Override
+        public void show() {
+            System.out.println("这是春天");
+        }
+    },
+    SUMMER("夏天", "烈日当空"){
+        @Override
+        public void show() {
+            System.out.println("这是夏天");
+        }
+    },
+    AUTUMN("秋天", "秋高气爽"){
+        @Override
+        public void show() {
+            System.out.println("这是秋天");
+        }
+    },
+    WINTER("冬天", "冰天雪地"){
+        @Override
+        public void show() {
+            System.out.println("这是冬天");
+        }
+    };
+
+
+    // 2.声明Season对象的属性
+    private final String seasonName;
+    private final String seasonDesc;
+
+    // 3.私有化类的构造器，并给对象属性赋值
+    private Season(String seasonName, String seasonDesc){
+        this.seasonName = seasonName;
+        this.seasonDesc = seasonDesc;
+    }
+
+    // 4.获取枚举类对象的属性
+    public String getSeasonName() {
+        return seasonName;
+    }
+
+    public String getSeasonDesc() {
+        return seasonDesc;
+    }
+}
-- 
Gitee


From 434897a75a218f0efa7afcde67473b16a423310c Mon Sep 17 00:00:00 2001
From: zenghongyi <277382367@qq.com>
Date: Wed, 30 Mar 2022 13:43:47 +0800
Subject: [PATCH 09/10] =?UTF-8?q?java=E9=AB=98=E7=BA=A7=20=E8=87=AA?=
 =?UTF-8?q?=E5=AE=9A=E4=B9=89=E6=B3=A8=E8=A7=A3?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 javase/src/main/java/com/hongyi/day5/MyAnnotation.java | 10 ++++++++++
 .../src/test/java/com/hongyi/day4/AnnotationTest.java  |  3 +++
 2 files changed, 13 insertions(+)
 create mode 100644 javase/src/main/java/com/hongyi/day5/MyAnnotation.java

diff --git a/javase/src/main/java/com/hongyi/day5/MyAnnotation.java b/javase/src/main/java/com/hongyi/day5/MyAnnotation.java
new file mode 100644
index 0000000..6896d43
--- /dev/null
+++ b/javase/src/main/java/com/hongyi/day5/MyAnnotation.java
@@ -0,0 +1,10 @@
+package com.hongyi.day5;
+
+/**
+ * @Author Kisugi Takumi
+ * @Date 2022/3/30 13:24
+ * @Version 1.0
+ */
+public @interface MyAnnotation {
+    String value() default "world";
+}
diff --git a/javase/src/test/java/com/hongyi/day4/AnnotationTest.java b/javase/src/test/java/com/hongyi/day4/AnnotationTest.java
index 8f13744..3799e65 100644
--- a/javase/src/test/java/com/hongyi/day4/AnnotationTest.java
+++ b/javase/src/test/java/com/hongyi/day4/AnnotationTest.java
@@ -1,5 +1,6 @@
 package com.hongyi.day4;
 
+import com.hongyi.day5.MyAnnotation;
 import org.junit.Test;
 
 /**
@@ -16,8 +17,10 @@ public class AnnotationTest {
         @SuppressWarnings("unused")
         int a = 10;
     }
+
 }
 
+@MyAnnotation(value = "hello")
 class Person{
     private String name;
     private int age;
-- 
Gitee


From f830cbf1e786af506ba0581cbb404f1ac88624df Mon Sep 17 00:00:00 2001
From: zenghongyi <277382367@qq.com>
Date: Wed, 30 Mar 2022 14:30:21 +0800
Subject: [PATCH 10/10] =?UTF-8?q?java=E9=AB=98=E7=BA=A7=20Collections?=
 =?UTF-8?q?=E5=B7=A5=E5=85=B7=E7=B1=BB?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../java/com/hongyi/day5/CollectionsTest.java | 69 +++++++++++++++++++
 1 file changed, 69 insertions(+)
 create mode 100644 javase/src/test/java/com/hongyi/day5/CollectionsTest.java

diff --git a/javase/src/test/java/com/hongyi/day5/CollectionsTest.java b/javase/src/test/java/com/hongyi/day5/CollectionsTest.java
new file mode 100644
index 0000000..c99e719
--- /dev/null
+++ b/javase/src/test/java/com/hongyi/day5/CollectionsTest.java
@@ -0,0 +1,69 @@
+package com.hongyi.day5;
+
+import org.junit.Test;
+
+import java.util.*;
+import java.util.stream.Collectors;
+
+/**
+ * @Author Kisugi Takumi
+ * @Date 2022/3/30 14:02
+ * @Version 1.0
+ */
+public class CollectionsTest {
+    @Test
+    public void test0(){
+        List<Integer> list = new ArrayList<>();
+        list.add(123);
+        list.add(43);
+        list.add(0);
+        list.add(-97);
+        list.add(765);
+        System.out.println(list); // [123, 43, 0, -97, 765]
+        // 倒序处理
+        Collections.reverse(list);
+        System.out.println(list); // [765, -97, 0, 43, 123]
+        // 升序排序
+        Collections.sort(list);
+        System.out.println(list); // [-97, 0, 43, 123, 765]
+        // 定制排序
+        Collections.sort(list, new Comparator<Integer>() {
+            // 按照降序排序
+            @Override
+            public int compare(Integer o1, Integer o2) {
+                return -Integer.compare(o1, o2);
+            }
+        });
+        System.out.println(list); // [765, 123, 43, 0, -97]
+    }
+
+    @Test
+    public void test1(){
+        List<Integer> list = new ArrayList<>();
+        list.add(123);
+        list.add(43);
+        list.add(0);
+        list.add(-97);
+        list.add(765);
+        // 错误的写法：Source does not fit in dest
+        // List<Integer> dest = new ArrayList<>();
+        // Collections.copy(dest, list);
+
+        List<Integer> dest = Arrays.asList(new Integer[list.size()]);
+        System.out.println(dest.size()); // 5
+        Collections.copy(dest, list);
+        System.out.println(dest); // [123, 43, 0, -97, 765]
+    }
+
+    @Test
+    public void test2(){
+        List<Integer> list = new ArrayList<>();
+        list.add(123);
+        list.add(43);
+        list.add(0);
+        list.add(-97);
+        list.add(765);
+        // 返回一个线程安全的list1
+        List<Integer> list1 = Collections.synchronizedList(list);
+    }
+}
-- 
Gitee