Java学习

package com.collection;

import org.junit.Test;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;

public class CollectionTest1 {
    
    @Test
    public void test(){

        Collection coll = new ArrayList();
        coll.add(123);
        coll.add(456);
        coll.add(new String("Tom"));
        coll.add(false);
//        Person p = new Person("Jerry",20);
//        coll.add(p);
        coll.add(new Person("Jerry",20));

        // contain 判断时会调用obj的equal方法
        boolean contains = coll.contains(123);
        System.out.println(contains);
        System.out.println(coll.contains(new String("Tom")));
//        System.out.println(coll.contains(p));
        System.out.println(coll.contains(new Person("Jerry",20)));

        // containsAll
        Collection coll1 = Arrays.asList(123,456);
        System.out.println(coll.containsAll(coll1));
    }
}

    // 向Collection接口的实现类的对象中添加数据obj时，要求obj所在类要重写equals()
    @Test
    public void test2(){
        // remove
        Collection coll = new ArrayList();
        coll.add(123);
        coll.add(456);
        coll.add(new Person("Jerry",20));
        coll.add(new String("Tom"));
        coll.add(false);

        coll.remove(123);
        System.out.println(coll);

        coll.remove(new Person("Jerry",20));

        //removeAll 取差集
        Collection coll1 = Arrays.asList(123,4567);
        coll.remove(coll1);
        System.out.println(coll);
    }
    @Test
    public void test3(){
        Collection coll = new ArrayList();
        coll.add(123);
        coll.add(456);
        coll.add(new Person("Jerry",20));
        coll.add(new String("Tom"));
        coll.add(false);

        //retainAll 取交集
//        Collection coll1 = Arrays.asList(123,456,789);
//        coll.retainAll(coll1);
//        System.out.println(coll);

        //equals(Object obj)
        Collection coll1 = new ArrayList();
        coll1.add(123);
        coll1.add(456);
        coll1.add(new Person("Jerry",20));
        coll1.add(new String("Tom"));
        coll1.add(false);

        System.out.println(coll.equals(coll1));

    }

    @Test
    public void test4(){
        Collection coll = new ArrayList();
        coll.add(123);
        coll.add(456);
        coll.add(new Person("Jerry",20));
        coll.add(new String("Tom"));
        coll.add(false);

        //hashCode() 返回当前对象的哈希值
        System.out.println(coll.hashCode());
        //集合 --> 数组 toArray
        Object[] arr = coll.toArray();
        for (int i = 0; i < arr.length; i++) {
            System.out.println(arr[i]);
        }
        // 数组 --> 集合 调用Arrays类的静态方法
        List list = Arrays.asList(new String[]{"AA", "BB", "CC"});
        System.out.println(list);

        List integers = Arrays.asList(123, 456);
        System.out.println(integers);
        
        //iterator
        
    }