Java-Collection

 集合的简单操作

 

package com.util;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

public class CollectionsPractice {
    public static void main(String[] args) {
        CollectionsPractice collections = new CollectionsPractice();
        // collections.listConnection();
        //collections.connectionSet();
        collections.mapConnection();
    }

    public void listConnection() {
        List<Integer> list = new ArrayList<Integer>();
        for (int i = 0; i < 100; i++) {
            list.add(i);
        }
        // list.clear(); //清空list
        if (!list.isEmpty()) {
            for (Integer list1 : list) {
                System.out.print(list1 + "  ");
            }
        } else {
            System.out.println("list为空……");
        }
    }

    public void connectionSet() {
        Set<Integer> set = new HashSet<Integer>();
        for (int i = 0; i < 100; i++) {
            set.add(i);
        }
        // set.clear(); //清空set
        if (!set.isEmpty()) {
            for (Integer sets : set) {
                System.out.print(sets + "   ");
            }
        } else {
            System.out.println("set为空……");
        }
        System.out.println(set.contains(99));// 判断99是否存在 是返回true
    }

    public void mapConnection() {
        Map<Integer, String> map = new HashMap<Integer, String>();
        for (int i = 0; i < 8; i++) {
            map.put(i, i+"值");
        }
        for (Map.Entry<Integer, String> map2:map.entrySet()) {
            System.out.println(map2.getKey()+map2.getValue());
        }
        for(Integer map3:map.keySet()) {
             System.out.println(map3+"====================="+map.get(map3));
        }
        map.clear();
        if(!map.isEmpty()) {
            Set<Integer> set = map.keySet();
            Iterator<Integer>  iterator = set.iterator();
            while(iterator.hasNext()) {
                Integer keyInteger = iterator.next();
                System.out.println("key："+keyInteger+"   value："+map.get(keyInteger));
            }
        }else{
            System.out.println("map为空……");
        }
    }
}