JavaSE--for each

 1 package foreach;
 2 
 3 public class ForeachDemo1 {
 4     
 5     public static void main(String[] args) {
 6         Object[] objs = new Test[5];
 7         int i = 0;
 8         //for each的简洁使得我喜欢这种使用方式
 9         for(Object obj : objs) {
10             obj = new Test(i + "");
11             System.out.println(objs[i++]);//2
12         }
13         System.out.println(objs[2]);//1
14     }
15 
16 }
17 
18 class Test {
19     
20     private String value;
21     
22     public Test(String value) {
23         this.value = value;
24     }
25 
26     public String getValue() {
27         return value;
28     }
29 
30     public void setValue(String value) {
31         this.value = value;
32     }
33 
34     @Override
35     public String toString() {
36         return "Test [value=" + value + "]";
37     }
38     
39     
40     
41 }

 1 package foreach;
 2 
 3 public class Apple1 {
 4     
 5     public static void main(String[] args) {
 6         Thread[] t1 = new T1[3];
 7         Thread[] t2 = new T2[2];
 8         
 9         for(Thread t : t1) {
10             t = new T2();//大概就是这样，原代码是生产者消费者交替打印而产生的线程无限等待
11                         //然而这样做并没毛病
12             //-->等价于
13             //Thread t = t1[0]
14             //t = new T2()
15             //t.start()
16             //这当然没问题了
17             t.start();
18         }
19         
20         t1[0] = new T2();
21         //但是这样的话 就抛异常了【当你试图将错误类型的对象存储到一个对象数组时抛出的异常】
22         //声明的空间和实际new的类型不一致
23     }
24 
25 }
26 
27 class T1 extends Thread {
28     
29     //...
30 
31     @Override
32     public void run() {
33         // TODO Auto-generated method stub
34     }
35 
36 }
37 
38 class T2 extends Thread {
39     
40     //..
41 
42     @Override
43     public void run() {
44         // TODO Auto-generated method stub
45     }
46 
47 }

 1 package foreach;
 2 
 3 public class Demo2 {
 4     
 5     public static void main(String[] args) {
 6         String[] strs = new String[3];
 7         
 8         for(String s : strs) {    
 9             s = "1";
10         }
11         
12         System.out.println(strs[0]);
13     }
14 
15 }