关于Java 拷贝数组方法 Arrays.copyOf() 是地址传递还是值传递

Posted 2020-09-17 wqkant

 

基本元素为对象时,浅拷贝，拷贝引用（ArrayList 的clone()调用Arrays.copyof()，官方文档注明为浅拷贝）

class A{
            int a;
            public A(int a){
                this.a=a;
            }
            public String toString(){
                
                return a+"";
            }
        }
        
        A[] kk=new A[2];
        kk[0]=new A(1);
        kk[1]=new A(2);
        
        A[] kkk=Arrays.copyOf(kk,2);
        System.out.println(kk==kkk);
        System.out.println(kk.equals(kkk));
        System.out.println(Arrays.toString(kk));
        System.out.println(Arrays.toString(kkk));
        kk[0].a=555555;
        
        System.out.println(Arrays.toString(kk));
        System.out.println(Arrays.toString(kkk));

/*

false
false
[1, 2]
[1, 2]
[555555, 2]
[555555, 2]

为值时，

        int[] a=new int[2];
        a[0]=11;
        a[1]=2;
        int[] b=Arrays.copyOf(a, 2);
        a[1]=3333333;
        System.out.println(Arrays.toString(a));
        System.out.println(Arrays.toString(b));  
/*output

[11, 3333333]

[11, 2]