From b442e223ebb680f683f84f3ed594df27e4e76d2b Mon Sep 17 00:00:00 2001
From: jlhde123 ASUS <472327024@qq.com>
Date: Thu, 9 Mar 2017 19:56:53 +0800
Subject: [PATCH] =?UTF-8?q?=E6=96=B0=E5=A2=9E=20ArrayList=20=E7=9A=84?=
 =?UTF-8?q?=E5=AD=A6=E4=B9=A0?=
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---
 .../com/jlh/viewer/ArrayListTestList.java     | 25 +++++++++++++++++++
 1 file changed, 25 insertions(+)
 create mode 100644 jlh/src/main/java/com/jlh/viewer/ArrayListTestList.java

diff --git a/jlh/src/main/java/com/jlh/viewer/ArrayListTestList.java b/jlh/src/main/java/com/jlh/viewer/ArrayListTestList.java
new file mode 100644
index 0000000..21c4eaf
--- /dev/null
+++ b/jlh/src/main/java/com/jlh/viewer/ArrayListTestList.java
@@ -0,0 +1,25 @@
+package com.jlh.viewer;
+
+import java.util.ArrayList;
+
+/**
+ * com.jlh.viewer
+ * Created by ASUS on 2017/3/9.
+ * 19:42
+ */
+public class ArrayListTestList {
+    public static void main(String[] args) {
+        //一般实现了RandomAccess接口的类用loop快，其余的用iterator快， RandomAccess是空接口，仅做标志，代表该类是通过数组实现，可以快速随机访问
+        // 类似与Serializable接口也仅仅做标记，其中serialVersionUID代表类的版本号，版本号不符合时以便抛出异常，一旦修改版本号就代表对之前版本的类不再支持
+        //list 与一般colleciton不同的地方多了个Listiterator 比iterator 多了可以修改的支持   iterator是快速失败的核心
+        //capacity 默认10  默认1.5倍扩容，如果1.5倍还是要小直接扩容至最小的需要大小  vector 为2倍 且为线程安全
+        int capacity=16;
+        ArrayList<Integer> arrayList = new ArrayList<>(capacity);
+        for (int i=0;i<17;i++){
+            arrayList.add(i);
+        }
+        //压缩多余空余空间
+        arrayList.trimToSize();
+        System.out.println(arrayList.toArray().length);
+    }
+}
-- 
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