reference copy

main.java

package com.alex.methods;

import java.util.Arrays;

public class JavaApplication1 {
    
    static void changeArray(int[] ar) {
        ar[0] = 100;
    }
    
    public static void main(String[] args) {
        int[] ar = {1, 2, 3};
        changeArray(ar);
        System.out.println(Arrays.toString(ar)); // 100 2 3
    }
}