Analysis of the difference between value passing and reference passing in Java

Pass value -- pass basic data type parameters

public    class           PassValue{
    static void exchange(int a, int b){//Static method, swap the values of a and b
        int temp;
        temp = a;
        a = b;
        b = temp;
    }
    public static void main(String[] args){
       int i = 10;
       int j = 100;
       System.out.println("before call: " + "i=" + i + "t" + "j = " + j);//Before the call
        exchange(i, j);                                                                    //The main method can only call static methods
        System.out.println("after call: " + "i=" + i + "t" + "j = " + j);//After the call
    }
}

Operation results:

        before call: i = 10        j = 100
        after    call: i = 10        j = 100
 

Description: when calling exchange(I, j), the actual parameters I and j respectively pass values to the corresponding formal parameters a and b. when executing the method exchange(), the change of the values of the formal parameters a and b does not affect the values of the actual parameters I and j, and the values of I and j do not change before and after the call.
Passing a reference -- object as an argument

class Book{
    String name;
    private folat price;
    Book(String n,    float ){                //A constructor
        name = n;
        price = p;
    }
    static  void  change(Book a_book,    String n,    float p){    //Static method, object as parameter
            a_book.name = n;
            a_book.price = p;
    }
    public void output(){        //Instance method, output object information
        System.out.println("name: " + name + "t" + "price: " + price);
    }
}
 public class PassAddr{
    public static void main(String [] args){
        Book b = new Book("java2",    32.5f);
        System.out.print("before call:t");        //Before the call
        b.output();
        b.change(b,    "c++",    45.5f);            //Reference passing, passing a reference to object b, changing the value of object b
        System.out.print("after call:t");            //After the call
        b.output();
    }
}

Operation results:

        before    call:    name:java2        price:32.5
        after       call:    name:c++          price:45.5

Description: when calling change(b,"c++",45.5f), object b is used as the actual parameter and the reference is passed to the corresponding formal parameter a_book. In fact, a_book also points to the same object, that is, the object has two reference names: b and a_book. When the method change() is executed, the operation on the formal parameter a_book is the operation on the actual parameter b.