java复制

一个基本类：

package ddemo;

public class A {
    private String str;
    private int count;

    public A(String str,int count){
        this.str = str;
        this.count = count;
    }

    public A(){

    }

    public String getStr() {
        return str;
    }

    public int getCount() {
        return count;
    }

    public void setStr(String str) {
        this.str = str;
    }

    public void setCount(int count) {
        this.count = count;
    }
}

一个带有计数器的类：

package ddemo;

public class Acount implements Cloneable {
    public static int count = 0;
    private int index;

    public Acount() {
        this.index = count;
        count ++;
    }

    public int getIndex(){
        return index;
    }

    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }
}

一个带有copy函数的类：

package ddemo;

public class Acopy {
    public static int count;
    private int index;
    private String str;
    public Acopy(){
        this.index = count;
        count ++;
    }
    public Acopy(String str){
        this.str = str;
        this.index = count;
        count++;
    }

    public String getStr(){
        return this.str;
    }
    public int getIndex(){
        return this.index;
    }

    public void setIndex(int index) {
        this.index = index;
    }

    public void setStr(String str) {
        this.str = str;
    }

    public Acopy copy(){
        Acopy acopy = new Acopy(this.str);
        return acopy;
    }
}

Demo:

package ddemo;

/**
 *  这是一个测试类
 * */

public class Demo1 {
    public static void main(String[] args) throws CloneNotSupportedException {
        A a1 = new A();
        A a2 = a1;

        //1.    结果显示，a2只是a1的引用
        System.out.println(a1);
        System.out.println(a2);

        //2.    一个每次实例化一个对象就计数的类
        Acount acount1 = new Acount();
        Acount acount2 = new Acount();
        Acount acount3 = new Acount();
        System.out.println(acount1.getIndex());
        System.out.println(acount2.getIndex());
        System.out.println(acount3.getIndex());
        System.out.println(Acount.count);

        //2.    通过clone会绕开构造函数，从而使得计数器失效
        Acount acount4 = (Acount) acount2.clone();
        System.out.println(acount4.getIndex());


        //3.    一个自带copy函数的类
        System.out.println("==========================================");
        Acopy acopy1 = new Acopy("Hello1");
        Acopy acopy2 = new Acopy("Hello2");
        Acopy acopy3 = new Acopy("Hello3");
        Acopy acopy4 = acopy1.copy();
        System.out.println(acopy1.getIndex()+acopy1.getStr());
        System.out.println(acopy2.getIndex()+acopy2.getStr());
        System.out.println(acopy3.getIndex()+acopy3.getStr());
        System.out.println(acopy4.getIndex()+acopy4.getStr());




    }
}

result:

ddemo.A@4554617c
ddemo.A@4554617c
0
1
2
3
1
==========================================
0Hello1
1Hello2
2Hello3
3Hello1