java - swap function

Question

In the following code, the effect of exchanging two objects is not achieved
The output result is 3:4
Logically speaking, aren't all references in Java? You should be able to exchange objects directly!
Please explain my error and give a solution.
I hope the output result is 4:3
class Int
{

public int x;

}

public class Hello {

void swap(Int a,Int b)
{
    Int t=a;
    a=b;
    b=t;
}
public static void main(String[] args) {
    
    Hello hello=new Hello();
    Int a=new Int();
    Int b=new Int();
    a.x=3;
    b.x=4;
    hello.swap(a,b);
    System.out.println(a.x+":"+b.x);
}

}

Answer 1

In the Java world, the input parameters of functions or methods are passed through value copy:

原始类型(char，int，double等）都是通过直接拷贝变量值传参；
对象类型都是通过引用拷贝(跟C++中引用不同)传参，通过该引用能够更改其指向的对象内部值，但是更改该引用值，仅对函数内部可见，函数外部的实参依然没有改变；

Normally, java cannot implement it.
And the inside of the int object private final int value; is final