java-based: the value of the method call is passed call by value, and transmits the copy of the value of the parameter, rather than a reference

public class TestExtends {
    public  static void main(String[]args){
        int s = 10;
        System.out.println(System.identityHashCode(s));
        s=3*s;
        int num = 30;
        System.out.println(System.identityHashCode(s));
        System.out.println(System.identityHashCode(num));
}

　　

Export

460141958
1163157884
1163157884

　　

java-core  P121 

The method of passing parameters to the java, always call by value call by value.

In the method, if the parameter is the object that the operation is a copy of the referenced object.

If the parameter is a value, the value is a copy operation .

public class TestExtends {
    public  static void main(String[]args){
        A a =new A("bob");
        A b = new A("lucy");
        a.swap(a,b);
        System.out.println(a.getName()+" "+b.getName());
        A temp = new A("");
        temp=a;
        a=b;
        b=temp;
        System.out.println(a.getName()+" "+b.getName());
        int i =1;
        int j = 2;
        a.swap2(i,j);
        System.out.println(i+" "+j);
    }
}
class A{
    public int x=1;
    void swap(A a,A b){
        A temp = new A("---");
        temp=a;
        a=b;
        b=temp;
    }
    void swap2(int a ,int b){
        int c = 0;
        c=a;
        a=b;
        b=c;
    }
    private String  name;
    public  A(String name){
        this.name = name;
    }
    public String getName(){
        return name;
    }
}

　

bob lucy
lucy bob
1 2