集合（不常用）

￡神魔★判官ぃ 2022-07-14 14:27 201阅读 0赞

## HashSet ##

package com.hz.test;
    
    import java.util.HashSet;
    import java.util.Iterator;
    
    class R{
        int count;
        public R(int count) {
    
            this.count = count;
        }
    
        public String toString() {
            return "R(count属性："+count+")";
        }
    
        public boolean equals(Object obj) {
    
            if(obj instanceof R){
                R r = (R)obj;
                if(r.count == this.count){
                    return true;
                }
            }
            return false;
        }
    
        public int hashCode() {
    
            return this.count;
        }
    }
    public class TestHashSet {
    
        public static void main(String[] args) {
            HashSet hs = new HashSet();
            hs.add(new R(5));
            hs.add(new R(-3));
            hs.add(new R(9));
            hs.add(new R(2));
            //打印HashSet集合，集合元素没用重复
            System.out.println(hs);
            //取出第一个元素
            Iterator it = hs.iterator();
            R first = (R) it.next();
            //为第一个元素count属性赋值
            first.count = -3;
            //再次输出HashSet集合，集合元素有重复的元素
            System.out.println(hs);
            //
            hs.remove(new R(-3));
    
            System.out.println(hs);
    
            System.out.println("hs是否包含count为-3的R对象？"+hs.contains(new R(-3)));
            System.out.println("hs是否包含count为5的R对象？"+hs.contains(new R(5)));
        }
    }

## TreeSet ##

package com.hz.test;
    
    import java.util.Comparator;
    import java.util.TreeSet;
    import java.util.function.Function;
    import java.util.function.ToDoubleFunction;
    import java.util.function.ToIntFunction;
    import java.util.function.ToLongFunction;
    
    /**
     * 定制排序
     * @author ztw
     *
     */
    class M{
        int age;
        public M(int age) {
    
            this.age = age;
        }
        @Override
        public String toString() {
            return "M对象（age:"+age+"）";
        }
    }
    public class TestTreeSet3 {
        
    
        public static void main(String[] args) {
            TreeSet ts = new TreeSet(new Comparator() {
    
                public int compare(Object o1, Object o2) {
                    M m1 = (M) o1;
                    M m2 = (M) o2;
                    if(m1.age>m2.age){
                        return -1;
                    }else if(m1.age==m2.age){
                        return 0;
                    }else{
                        return 1;
                    }
    
                }
    
            });
    
            ts.add(new M(5));
            ts.add(new M(-3));
            ts.add(new M(9));
            System.out.println(ts);
    
        }
    }

package com.hz.test;
    
    import java.util.Set;
    import java.util.TreeSet;
    
    public class TestTreeSetCommon {
    
        public static void main(String[] args) {
    
            TreeSet nums = new TreeSet();
            //向TreeSet添加四个Interger对象
            nums.add(5);
            nums.add(2);
            nums.add(10);
            nums.add(-9);
            //输出集合元素，看到集合元素已经处于排序状态
            System.out.println(nums);
            //输出集合里的第一个元素
            System.out.println(nums.first());
            System.out.println(nums.last());
            System.out.println(nums.headSet(4));
            System.out.println(nums.tailSet(5));
            System.out.println(nums.subSet(-3, 4));
        }
    }

输出结果：

> \[-9, 2, 5, 10\]  
> \-9  
> 10  
> \[-9, 2\]  
> \[5, 10\]  
> \[2\]

## LinkedHashSet ##

package com.hz.test;
    
    import java.util.LinkedHashSet;
    import java.util.Set;
    
    public class TestLinkedHashSet {
    
        public static void main(String[] args) {
            Set books = new LinkedHashSet();
    
            books.add("Struts权威指南");
            books.add("轻量级Java2EE");
            //删除
            books.remove("Struts权威指南");
            books.add("Struts权威指南");
            for (Object object : books) {
                System.out.println(object);
            }
        }
    }

输出结果：

> 轻量级Java2EE  
> Struts权威指南

## EnumSet ##

package com.hz.test;
    
    import java.util.EnumSet;
    
    enum Season{
        SPRING,SUMMER,FALL,WINTER
    }
    public class EnumSetDemo {
    
        public static void main(String[] args) {
            //创建一个EnumSet集合，集合元素就是Season枚举类的全部枚举值
            EnumSet es1 = EnumSet.allOf(Season.class);
            System.out.println(es1);
            EnumSet es2 = EnumSet.noneOf(Season.class);
            System.out.println(es2);
            es2.add(Season.WINTER);
            es2.add(Season.SPRING);
            System.out.println(es2);
        }
    }

输出结果：

> \[SPRING, SUMMER, FALL, WINTER\]  
> \[\]  
> \[SPRING, WINTER\]

## HashMap ##

package com.hz.hashmap;
    
    import java.util.HashMap;
    import java.util.Iterator;
    import java.util.Map;
    import java.util.Map.Entry;
    import java.util.Set;
    
    import javax.swing.text.html.parser.Entity;
    
    public class Test {
    
        public static void main(String[] args) {
    
            HashMap<String, String> hashMap = new HashMap<>();
            hashMap.put("张三", "89");
            hashMap.put("李四", "70");
            hashMap.put("王五", "88");
            hashMap.put("赵六", "99");
    
    //      Set<Entry<String, String>> set = hashMap.entrySet();
    //      Iterator<Entry<String, String>> it = set.iterator();
    //      while(it.hasNext()){
    //          Entry<String, String> entry = it.next();
    //          String key = entry.getKey();
    //          String value = entry.getValue();
    //          System.out.println(key + "=" + value);
    //      }
    //      for (Entry<String, String> entry  : hashMap.entrySet()) {
    //          
    //          System.out.println(entry.getKey() + "=" + entry.getValue());
    //      }
    
            Set<String> set = hashMap.keySet();
            Iterator<String> it = set.iterator();
            while(it.hasNext()){
                String key = it.next();
                String value = hashMap.get(key);
    
                System.out.println(key + "＝" + value);
    
            }
        }
    }

输出结果：

> 李四＝70  
> 张三＝89  
> 王五＝88  
> 赵六＝99

这里写代码片