Java类集（List、Set、Map等）

深藏阁楼爱情的钟 2022-08-21 07:56 155阅读 0赞

类集（Collection）就是一个动态的对象数组。Java的类集框架使程序处理对象组的方法标准化。在Java 2出现之前，Java提供了一些专门的类如Dictionary、Vector、Stack和Properties去存储和操作对象组。尽管这些类非常有用，它们却缺少一个集中，统一的主题。因此例如说使用Vector的方法就会与使用Properties的方法不同。以前的专门的方法也没有被设计成易于扩展和能适应新的环境的形式。而类集解决了这些（以及其他的一些）问题。

![这里写图片描述][20160424103812677]

![这里写图片描述][20160424103946084]

import java.util.ListIterator;
    import java.util.Set;
    import java.util.TreeSet;
    
    //List是Collection的子接口，可以保存各个重复的元素
    public class MyListSetDemo {
        public static void main(String[] args) {
            List<String> list = new ArrayList<String>();
            list.add("hello");
            list.add("world");
            list.add("nihao");
            list.add("nihao");
            System.out.println(list);
    
            // 迭代输出:Iterator
            Iterator<String> ite1 = list.iterator();
            while (ite1.hasNext()) {
                System.out.print(ite1.next() + "、");
            }
            System.out.println();
    
            // 双向迭代输出:ListIterator
            ListIterator<String> ite2 = list.listIterator();
            while (ite2.hasNext()) {
                System.out.print(ite2.next() + "、");
            }
            System.out.println();
            while (ite2.hasPrevious()) {
                System.out.print(ite2.previous() + "、");
            }
            System.out.println();
    
            // foreach方法的输出
            for (String s : list) {
                System.out.print(s + "、");
            }
            System.out.println();
    
            //List接口中能加入重复元素,List<String> list=new ArrayList<String>();方法不再赘述
    
            //Set接口中不能加入重复元素
            // HashSet 不重复无序
            Set<String> mSet1 = new HashSet<String>();
            mSet1.add("qq");
            mSet1.add("qq");
            mSet1.add("weixin");
            mSet1.add("feixin");
            System.out.println(mSet1);
    
             TreeSet 不重复有序/
            Set<String> mSet2 = new TreeSet<String>();
            mSet2.add("qq");
            mSet2.add("qq");
            mSet2.add("weixin");
            mSet2.add("feixin");
            System.out.println(mSet2);
    
        }
    
    }

//简单的栈和队列
    package MyClassCollection;
    
    import java.util.LinkedList;
    import java.util.Stack;
    
    public class StackDemo {
        public static void main(String[] args) {
    
            Stack<String> stack = new Stack<String>();
            System.out.print(stack.push("A") + "、");
            System.out.print(stack.push("B") + "、");
            System.out.print(stack.push("C") + "、");
            System.out.println();
            System.out.print(stack.pop() + "、");
            System.out.print(stack.pop() + "、");
            System.out.print(stack.pop() + "、");
    
            System.out.println();
    
            LinkedList<String> sequence = new LinkedList<String>();
            System.out.print(sequence.offer("A") + "、");
            System.out.print(sequence.offer("B") + "、");
            System.out.print(sequence.offer("C") + "、");
            System.out.println();
            System.out.print(sequence.pop() + "、");
            System.out.print(sequence.pop() + "、");
            System.out.print(sequence.pop() + "、");
    
        }
    
    }

//Map专门用来保存<key,value>的内容
    package MyClassCollection;
    
    import java.util.Collection;
    import java.util.HashMap;
    import java.util.IdentityHashMap;
    import java.util.Iterator;
    import java.util.Map;
    import java.util.Set;
    import java.util.TreeMap;
    import java.util.WeakHashMap;
    
    public class MyMapDemo {
        public static void main(String args[]) {
            // Map的一些基本属性
            Map<String, String> map = new HashMap<String, String>();
            map.put("bj1", "bbbjjj1");
            map.put("bj2", "bbbjjj2");
            map.put("bj3", "bbbjjj3");
            String val = map.get("bj1");
            System.out.println("bj1= " + val);
            if (map.containsKey("bj1") && map.containsValue("bbbjjj1")) {
    
                System.out.print("bj1键存在 ");
                System.out.println("bbbjjj1值存在");
            }
    
            // 键排序
            Set<String> keys = map.keySet();
            Iterator<String> ite1 = keys.iterator();
            while (ite1.hasNext()) {
                System.out.print(ite1.next() + "、");
            }
            System.out.println();
    
            // 值排序
            Collection<String> values = map.values();
            Iterator<String> ite2 = values.iterator();
            while (ite2.hasNext()) {
                System.out.print(ite2.next() + "、");
            }
            System.out.println();
    
            // TreeMap演示,默认排好序列
            Map<String, String> treeMap = new TreeMap<String, String>();
            treeMap.put("tree1", "ttteee1");
            treeMap.put("tree5", "ttteee5");
            treeMap.put("tree3", "ttteee3");
            treeMap.put("tree3", "ttteee3");
            System.out.println("TreeMap演示 " + treeMap);
    
            // WeakHashMap演示
            Map<String, String> weakMap = new WeakHashMap<String, String>();
            weakMap.put(new String("hello"), new String("你好"));
            weakMap.put(new String("ok"), new String("好的"));
            weakMap.put(new String("yes"), new String("是的"));
            weakMap.clear();
            weakMap.put(new String("good"), new String("漂亮"));
            weakMap.put(new String("good"), new String("漂亮"));
            System.out.println("WeakHashMap演示 " + weakMap);
    
            Map<String, String> identityMap = new IdentityHashMap<String, String>();
            identityMap.put(new String("hello"), new String("你好"));
            identityMap.put(new String("hello"), new String("你好"));
            identityMap.put(new String("yes"), new String("是的"));
            System.out.println("IdentityHashMap演示 " + identityMap);
    
        }
    
    }

[20160424103812677]: /images/20220724/afbdcda15f324eaeaea96981c1b9d3c1.png
[20160424103946084]: /images/20220724/f100818ff746463aa1fddf9c946cb119.png