Java 数组复制之clone方法

Posted 2020-11-23 zhuanjiao

一、源码

public class Test1 {
    public static void main(String[] args) {
        // Student[] arrs = new Student[] { new Student() { id = "22" } }; C# 可以简写法，Java不支持
        Student[] arrs = new Student[1];
        Student st = new Student();
        st.id = 12;
        st.name = "qwe";
        arrs[0] = st;
        Student[] arrss = arrs.clone();
        System.out.println(arrs == arrss);
        System.out.println(arrs.equals(arrss));
        arrss[0].id = 56;
        for (int i = 0; i < arrs.length; i++) {
            System.out.println(arrs[i].id + arrs[i].name);
        }
        for (int i = 0; i < arrss.length; i++) {
            System.out.println(arrss[i].id + arrss[i].name);
        }
        System.out.println("-------------自定义对象类型数组clone-------------");

        Student[] arrst1 = new Student[1];
        Student st1 = new Student();
        st1.id = 162;
        st1.name = "qkkj";
        arrst1[0] = st1;
        Student[] arrst2 = arrst1;
        System.out.println(arrst1 == arrst2);
        System.out.println(arrst1.equals(arrst2));
        arrst2[0].id = 996;
        for (int i = 0; i < arrst1.length; i++) {
            System.out.println(arrst1[i].id + arrst1[i].name);
        }
        for (int i = 0; i < arrst2.length; i++) {
            System.out.println(arrst2[i].id + arrst2[i].name);
        }
        System.out.println("-------------自定义对象类型数组= 赋值-------------");

        var arr1 = new String[] { "we", "dfeffg" };
        var arr = arr1.clone();
        System.out.println(arr1 == arr);
        System.out.println(arr1.equals(arr));
        arr[1] = "ddddddddddddddd";
        for (int i = 0; i < arr.length; i++) {
            System.out.println(arr[i]);
        }
        for (int i = 0; i < arr1.length; i++) {
            System.out.println(arr1[i]);
        }
        System.out.println("------------字符串数组clone--------------");

        var arr11 = new String[] { "we", "dfeffg" };
        var arr111 = arr11;
        System.out.println(arr111 == arr11);
        System.out.println(arr111.equals(arr11));
        arr111[1] = "ddddddddddddddd";
        for (int i = 0; i < arr11.length; i++) {
            System.out.println(arr11[i]);
        }
        for (int i = 0; i < arr111.length; i++) {
            System.out.println(arr111[i]);
        }
        System.out.println("------------字符串数组=赋值--------------");

        var arr2 = new int[] { 232, 45 };
        var arr3 = arr2.clone();
        System.out.println(arr2 == arr3);
        System.out.println(arr2.equals(arr3));
        arr3[1] = 4444;
        for (int i = 0; i < arr2.length; i++) {
            System.out.println(arr2[i]);
        }
        for (int i = 0; i < arr3.length; i++) {
            System.out.println(arr3[i]);
        }
        System.out.println("------------数字类型数组clone--------------");

        var arr4 = new int[] { 23432, 44455 };
        var arr5 = arr4;
        System.out.println(arr4 == arr5);
        System.out.println(arr4.equals(arr5));
        arr4[1] = 6666;
        for (int i = 0; i < arr4.length; i++) {
            System.out.println(arr4[i]);
        }
        for (int i = 0; i < arr5.length; i++) {
            System.out.println(arr5[i]);
        }
        System.out.println("------------数字类型数组=赋值-----------------");
    }
}

class Student {
    public int id;
    public String name;

    public Student() {

    }

    public Student(String name, int id) {
        this.name = name;
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }
}

二、运行结果

false
false
56qwe
56qwe
-------------自定义对象类型数组clone-------------
true
true
996qkkj
996qkkj
-------------自定义对象类型数组= 赋值-------------
false
false
we
ddddddddddddddd
we
dfeffg
------------字符串数组clone--------------
true
true
we
ddddddddddddddd
we
ddddddddddddddd
------------字符串数组=赋值--------------
false
false
232
45
232
4444
------------数字类型数组clone--------------
true
true
23432
6666
23432
6666
------------数字类型数组=赋值-----------------

三、结果分析

　　1.clone复制，对于数组本身而言，它的元素是引用类型（字符串除外）的时候，本来数组每个元素中保存的就是对象的引用，所以，拷贝过来的数组自然而言也是对象的引用，所以对于数组对象元素而言，它又是浅拷贝；

　　2.clone复制，对于引用类型（字符串除外），改变其中一个中的值，会影响另外一个值，相当于“浅拷贝”；

　　3.clone复制，对于值类型、字符串，改变其中一个中的值，不会影响另外一个值，相当于“深拷贝”；

　　4.等号复值后修改一个后会影响另一个