java中hashCode()是什么

package com.tools;

import java.util.ArrayList;

public class HashCodeMeaning {

    public static void main(String[] args) {

        ArrayList list =  new ArrayList();

        int numberExist=0;

        //证明hashcode的值不是内存地址

        for (int i = 0; i < 10000; i++) {

            Object obj=new Object();

            if (list.contains(obj.toString())) {

                System.out.println(obj.toString() +"  exists in the list. "+ i);

                numberExist++;

            }

            else {

                list.add(obj.toString());

            }

        }

        System.out.println("repetition number:"+numberExist);

        System.out.println("list size:"+list.size());

        //证明内存地址是不同的。

        numberExist=0;

        list.clear();

        for (int i = 0; i < 10000; i++) {

            Object obj=new Object();

            if (list.contains(obj)) {

                System.out.println(obj +"  exists in the list. "+ i);

                numberExist++;

            }

            else {

                list.add(obj);

            }

        }

        System.out.println("repetition number:"+numberExist);

        System.out.println("list size:"+list.size());

    }

}