package com.shellway.javase;import java.util.ArrayList;import java.util.Collection;import java.util.HashSet;import java.util.Iterator;import java.util.List;import java.util.Map;import java.util.Set;import java.util.TreeMap;import org.junit.Test;public class TestCollection {    public static void print(Collection<? extends Object> c){    Iterator<? extends Object> it = c.iterator();    while (it.hasNext()) {      Object object = (Object) it.next();      System.out.println(object);    }  }    @Test  public void demo1(){    Set<String> set = new HashSet<String>();    set.add("AAA");    set.add("BBB");    set.add("CCC");    print(set);        //Set的第一種遍歷方式:利用Iterator    Iterator<String> it1 = set.iterator();    for (String ss : set) {      System.out.println(ss);    }    //Set的第一種遍歷方式:利用foreach    for (String sss : set) {      System.out.println(sss);    }        List<String> list = new ArrayList<String>();    list.add("DDDDD");    list.add("EEEEE");    list.add("FFFFF");    print(list);        //List的第一種遍歷方式:因為list有順序，利用size()和get()方法獲取    for (int i = 0; i < list.size(); i++) {      System.out.println(list.get(i));    }    //List的第二種遍歷方式：利用Iterator    Iterator<String> it = list.iterator();    while (it.hasNext()) {      System.out.println(it.next());    }    //List的第三種遍歷方式:利用foreach    for (String s2 : list) {      System.out.println(s2);    }        Map<String,String> map = new TreeMap<String, String>();    map.put("Jerry", "10000");    map.put("shellway", "20000");    map.put("Kizi", "30000");    print(map.entrySet());    //Map的第一種遍歷方式：先獲得key,再獲得值value    Set<String> sett = map.keySet();    for (String s : sett) {      System.out.println(s+":"+map.get(s));    }    //Map的第二種遍歷方式：獲得鍵值對    for (Map.Entry<String, String> entry : map.entrySet()) {      System.out.println(entry.getKey()+" : "+entry.getValue());    }  }}