Java 的传值原理，小例子

public class Test {

    static class B {
        public int i = 0;
        public String s = "0";
    }

    public static void main(String[] args) {
        int i = 0;
        change1(i);
        System.out.println(i);                         //0

        String a = "0";
        change2(a);
        System.out.println(a);                         //0

        B b1 = new B();
        change3(b1);
        System.out.println(b1.i + "   " + b1.s);       //100  100


        B b2 = new B();
        change4(b2);
        System.out.println(b2.i + "   " + b2.s);       //0  0
       
        int[] c1 = new int[]{0};
        change5(c1);
        System.out.println(c1[0]);                     //100
       
        int[] c2 = new int[]{0};
        change6(c2);
        System.out.println(c2[0]);                     //0
    }

    public static void change1(int i) {
        i = 100;
    }

    public static void change2(String a) {
        a = "100";
    }

    public static void change3(B b) {
        b.i = 100;
        b.s = "100";
    }

    public static void change4(B b) {
        b = new B();
        b.i = 100;
        b.s = "100";
    }
   
    public static void change5(int[] c) {       
        c[0] = 100;
    }
   
    public static void change6(int[] c) {
        c = new int[]{100};       
    }
}

 

评论

2 楼 黎明的曙光 2011-11-27  

其实都是传值，只不过有的时候传的是地址的副本有的是存储单元内容的副本

1 楼 393799950 2011-11-24  

我一直记得我们java老师说过，
java传输，是传值。传输的是指针的副本。

public static void main(){
  B b = new B();
  change4(b);
  Systen,out.println(b.i+"===="+b.s); // 都是0的原因
  // 如果java是传引用的话
  B b1 = new B();
  change4(b1);
  Systen,out.println(b1.i+"===="+b1.s); // 就都会变成100
}
public static void change4(B b) {
        b = new B();
        b.i = 100;
        b.s = "100";
    }