集合遍历的学习

wuhaidong

import java.util.ArrayList;import java.util.HashMap;import java.util.HashSet;import java.util.Iterator;import java.util.Map;import java.util.Set;public class T {public static void main(String[] args) {ArrayList al = new ArrayList();al.add("a");al.add("b");al.add("c");//Iterator iter = al.iterator();//while(iter.hasNext()){//String str = (String) iter.next();//System.out.println(str);//}//for(Iterator iter = al.iterator(); iter.hasNext();){//String str = (String) iter.next();//System.out.println(str);//}//HashSet hashSet = new HashSet();//hashSet.add("java");//hashSet.add(".net");//HashMap<String,String> map = new HashMap<String,String>();map.put("语文", "90");map.put("数学", "80");map.put("英语", "70");//if(map != null && !map.isEmpty()){//Set<String> set = map.keySet();//for(Iterator iter = set.iterator(); iter.hasNext();){//String key = (String) iter.next();//System.out.println(key);//}//}if(map != null && !map.isEmpty()){for(Iterator iter = map.entrySet().iterator();iter.hasNext();){Map.Entry entry = (Map.Entry)iter.next();String value = entry.getKey() +":"+ entry.getValue();System.out.println(value);}}}}