// JDK16的空指针异常长这样
Exception in thread "main" java.lang.NullPointerException: Cannot invoke "Object.toString()" because "localObj" is null
	at TestNull.main(TestNull.java:7)


// 代码长这样:
public class TestNull{
  public static void main(String... args){
    Object localObj = "renfufei";
    if("".length() < 10){
      localObj = null;
    }
    System.out.println(localObj.toString());
  }
}

// 执行的命令包括:
jenv versions
jenv local 16
javac -g TestNull.java
java TestNull


// 如果不加 -g
rm -f TestNull.class
javac TestNull.java
java TestNull

// 如果不加 -g, 局部变量表中没有存名字, 提示变为 "<local1>", "<local2>" 之类的
Exception in thread "main" java.lang.NullPointerException: Cannot invoke "Object.toString()" because "<local1>" is null
	at TestNull.main(TestNull.java:7)