Java编程思想读书笔记_第三章

本章提到的关于==的部分，一个完整的实验如下：

 class Test {
     public static void main(String[] args) {
         Integer i = new Integer(47);
         Integer j = new Integer(47);
         Integer i1 = 47;
         Integer j1 = 47;
         int i2 = new Integer(47);
         int j2 = new Integer(47);
         int i3 = 47;
         int j3 = 47;

         System.out.println( i == j ); //false
         System.out.println( i1 == j1 ); //true
         System.out.println( i2 == j2 ); //true
         System.out.println( i3 == j3 ); //true
         System.out.println( i1 == j2 ); //true
         System.out.println( i1 == j3 ); //true
         System.out.println( i2 == j3 ); //true

         String s = new String("java");
         String s1 = new String("java");
         String s2 = "java";
         String s3 = "java";
         System.out.println( s == s1 ); //false
         System.out.println( s2 == s3 ); //true
     }
 }

还有一点：虽然局部变量在定义之后必须初始化，否则会编译出错。但是对于数组，行为却不一样：

 class Test {
     public static void main(String[] args) {
         int i = 7;
         System.out.println("i = " + i);

         int[] a = new int[10];
         System.out.println("a[0] = " + a[0]); //0
     }
 }