第七篇 集合与容器(七)
集合的遍历
package com.zzp.demo; 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.Map.Entry; import java.util.Set; /** * * 测试迭代器的使用 * @author java * */ public class TestIterator { public static void main(String[] args) { // ListIterator(); // SetIterator(); MapIterator(); } public static void ListIterator(){ List<String> list = new ArrayList<>(); list.add("aa"); list.add("bb"); list.add("cc"); //遍历list for(Iterator<String> iter = list.iterator();iter.hasNext();){ String temp = iter.next(); System.out.println(temp); } } public static void SetIterator(){ Set<String> set = new HashSet<>(); set.add("aa"); set.add("bb"); set.add("cc"); //遍历set for(Iterator<String> iter = set.iterator();iter.hasNext();){ String temp = iter.next(); System.out.println(temp); } } public static void MapIterator(){ Map<Integer,String> map = new HashMap<>(); map.put(10, "aa"); map.put(20, "bb"); map.put(30, "cc"); //第一种方式遍历 Set<Entry<Integer, String>> ss = map.entrySet(); for(Iterator<Entry<Integer, String>> iter= ss.iterator();iter.hasNext();){ Entry<Integer, String> temp = iter.next(); System.out.println(temp.getKey()+"---"+temp.getValue()); } //第二种方式,直接获取key Set<Integer> keySet = map.keySet(); for(Iterator<Integer> Iter = keySet.iterator();Iter.hasNext();){ Integer temp = Iter.next(); System.out.println(temp +"---"+map.get(temp)); } } }
collections工具类的使用
package com.zzp.demo; import java.util.ArrayList; import java.util.Collections; import java.util.List; /** * * 测试collections类 * @author java * */ public class TestCollections { public static void main(String[] args) { List<String> list = new ArrayList<>(); for(int i=0;i<10;i++){ list.add("zhang"+i); } System.out.println(list); Collections.sort(list); System.out.println(list); Collections.reverse(list); System.out.println(list); Collections.shuffle(list); System.out.println(list); System.out.println(Collections.binarySearch(list, "zhang3"));//使用二分法查找,折半查找 } }