java 集合 HashSet 实现随机双色球 HashSet addAll() 实现去重后合并 HashSet对象去重 复写 HashCode()方法和equals方法 ArrayList去重

package com.swift.lianxi;

import java.util.HashSet;
import java.util.Random;

/*训练知识点：HashSet

训练描述
双色球规则:双色球每注投注号码由6个红色球号码和1个蓝色球号码组成。
红色球号码从1—33中选择；蓝色球号码从1—16中选择.请随机生成一注双色球号码*/

public class Test4 {

    public static void main(String[] args) {
        
        Random ran = new Random();
        HashSet<Integer> hong = new HashSet<Integer>();
        while(hong.size()<6) {
            int hongqiu=ran.nextInt(33)+1;
            hong.add(hongqiu);
        }
        int lanqiu=ran.nextInt(16)+1;
        System.out.print("双色球红球号码是:  ");
        for(Integer i:hong) {
            System.out.print(i+" ");
        }
        System.out.print(" 双色球篮球号码是: ");    
        System.out.print(lanqiu+"");    
    }
}

上边是双色球

下边是使用HashSet 去重后合并

package com.swift.lianxi;

import java.util.ArrayList;
import java.util.HashSet;

/*训练知识点:HashSet

训练描述
有2个ArrayList,元素如下: array1 = "a","b","a","c","d",array2 = "e","f","a","d","g",将两个集合重复项去除后合并成一个集合

操作步骤描述
    1.创建ArrayList array1
    2.使用add方法为array1存放对应的元素
    3.创建ArrayList array2
    4.使用add方法为array2存放对应的元素
    5.创建HashSet用于存放去除重复的元素
    6.遍历array1,获取到每个元素,将每个元素添加到HashSet中
    7.遍历array2,获取到每个元素,将每个元素添加到HashSet中
    8.输出HashSet中去除重复后的元素*/

public class Test3 {

    public static void main(String[] args) {
        ArrayList<String> array1 = new ArrayList<String>();
        array1.add("a");
        array1.add("b");
        array1.add("a");
        array1.add("c");
        array1.add("d");
        HashSet<String> set = new HashSet<String>();
        set.addAll(array1);
        ArrayList<String> array2 = new ArrayList<String>();
        array2.add("e");
        array2.add("f");
        array2.add("a");
        array2.add("d");
        array2.add("g");
        set.addAll(array2);
        for(String str:set) {
            System.out.println(str);
        }
        
        
    }
}

HashSet对象去重 复写 HashCode()方法和equals方法

package com.swift.lianxi;

import java.util.HashSet;
import java.util.LinkedHashSet;

/*定义一个Student类,包含名称,年龄,性别(姓名,年龄,性别完全相同视为同一学生)
创建10个Student对象,至少有两个学生姓名,年龄,性别完全相同. 把这10个学生添加到Set集合中,不可以重复,
遍历Set集合打印学生信息,使用两种方式*/

public class Demo3 {
        
    public static void main(String[] args) {
        
        HashSet<Students> set = new LinkedHashSet<Students>();
        set.add(new Students("zhangsan",20,"男"));
        set.add(new Students("lisi",22,"男"));
        set.add(new Students("wangwu",223,"男"));
        set.add(new Students("zhaoliu",1,"男"));
        set.add(new Students("tianqi",54,"男"));
        set.add(new Students("wangermazi",209,"男"));
        set.add(new Students("zhangsan",20,"男"));
        set.add(new Students("zhangsan",20,"男"));
        set.add(new Students("zhangsan",20,"男"));
        set.add(new Students("zhangsan",20,"男"));
        for(Students stu:set) {
            System.out.println(stu.toString());
        }
    }
    
}

/**
 * @author Advancing-Swift
 *
 */
class Students{
    
    private String name;
    private int age;
    private String sex;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
    public Students(String name, int age, String sex) {
        super();
        this.name = name;
        this.age = age;
        this.sex = sex;
    }
    public Students() {
        super();
    }
    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + age;
        result = prime * result + ((name == null) ? 0 : name.hashCode());
        result = prime * result + ((sex == null) ? 0 : sex.hashCode());
        return result;
    }
    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Students other = (Students) obj;
        if (age != other.age)
            return false;
        if (name == null) {
            if (other.name != null)
                return false;
        } else if (!name.equals(other.name))
            return false;
        if (sex == null) {
            if (other.sex != null)
                return false;
        } else if (!sex.equals(other.sex))
            return false;
        return true;
    }
    @Override
    public String toString() {
        return "Students [name=" + name + ", age=" + age + ", sex=" + sex + "]";
    }
    
}

  ArrayList去重

package com.swift.kaoshi;

import java.util.Iterator;
import java.util.LinkedList;

/*训练描述
已知数组存放一批QQ号码.QQ号码最长为11位,最短为5位
String[] strs = {"12345","67891",1"2347809933","98765432102","67891","12347809933"}
将该数组里面的所有qq号都存放在LinkedList中,将list中重复元素删除,将list中所有元素用两种方式打印出来

操作步骤描述
    1.定义QQ号码数组String[] strs
    2.创建LinkedList
    3.遍历strs获取每个qq号码
    4.判断LinkedList是否已经存在这个qq号码
    5.不存在这个qq号码则添加到LinkedList中
    6.增强for遍历LinkedList
    7.迭代器遍历LinkedList*/

/*
 * ArrayList也可以存放唯一的内容,通过toArray()转成数组,再通过contains判断集合中是否存在
 */
public class Test1 {

    public static void main(String[] args) {
        
        String[] strs = {"12345","67891","12347809933","98765432102","67891","12347809933"};
        LinkedList<String> qqhao = new LinkedList<String>();
        for(String str:strs) {
            if(!qqhao.contains(str)) {
                qqhao.add(str);
            }
        }
        Iterator<String> it = qqhao.iterator();
        while(it.hasNext()) {
            String qq = it.next();
            System.out.println(qq);
        }
    }
}