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  • 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);
            }
        }
    }
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  • 原文地址:https://www.cnblogs.com/qingyundian/p/8486523.html
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