Java的值傳遞和引用傳遞問題

String的對象是不可修改的，如果真正要達(dá)到改變字符串的效果，我們需要使用StringBuilder來替代String。

要想不改變原來的對象可以繼承Cloneable接口，實(shí)現(xiàn)其clone()

public class demo {

    public static void main(String[] args) {
        String x = new String("way");
        changeString(x);
        System.out.println(x);

        StringBuilder xx = new StringBuilder("ss");
        changeStringBuilder(xx);
        System.out.println(xx.toString());

        Dest dest = new Dest();
        dest.kk = 99;
        changeObject1(dest);
        System.out.println(dest.kk);
        changeObject2(dest);
        System.out.println(dest.kk);
    }

    public static void changeString(String x) {
        x = "even";
    }

    public static void changeStringBuilder(StringBuilder x) {
        x.append("even");
    }

    public static void changeObject1(Dest x) {
        Dest yy = null;
        try {
            yy = (Dest) x.clone();
        } catch (CloneNotSupportedException e) {
            e.printStackTrace();
        }
        yy.kk = 100;
    }
    public static void changeObject2(Dest x) {
        x.kk = 101;
    }
}

class Dest implements Cloneable {
    public Dest() {
    }

    public int kk = 0;

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