(主推)集合框架一：集合的概念|特点|与数组区别|框架图|共. - 黑马程序员技术交流社区

import java.util.*;
import static java.lang.System.*;//静态包导入
public class ArrayListDemo {
public static void main(String[] args) {
ArrayList<String> al = new ArrayList<String>();
//添加元素
al.add("张三");
al.add("李四");
al.add("王五");
al.add("赵六");
//for循环遍历集合
//注意：List中拥有自己特殊的方法get(int index)
for(int i = 0; i < al.size(); i++){
out.println("for..." + al.get(i));
}
//iterator的使用
Iterator<String> it = al.iterator();
while(it.hasNext()){
out.println("iterator..." + it.next());
}
//listIterator的使用
ListIterator<String> listIt = al.listIterator();
while(listIt.hasNext()){//顺向遍历
out.println("listIterator..." + listIt.next());
}
while(listIt.hasPrevious()){//逆向遍历
out.println("listIterator..." + listIt.previous());
}
//高级for循环
for(String name : al){
out.println("foreach..." + name);
}
}
}
//HashSet遍历：
import java.util.*;
import static java.lang.System.*;
public class HashSetDemo {
public static void main(String[] args) {
HashSet<Integer> hs = new HashSet<Integer>();
//添加元素
hs.add(3);
hs.add(5);
hs.add(7);
hs.add(6);//自动装箱
//iterator的使用
Iterator<Integer> it = hs.iterator();
while(it.hasNext()){
out.println("iterator..." + it.next());
}
//高级for循环
for(Integer num : hs){
out.println("foreach..." + num);
}
}
}
//HashMap遍历：
import java.util.*;
import static java.lang.System.*;
public class HashMapDemo {
public static void main(String[] args) {
HashMap<String,Integer> hm = new HashMap<String,Integer>();
//添加元素
hm.put("zxj", 22);
hm.put("wxp", 19);
hm.put("hyd", 20);
hm.put("lv", 11);
//keySet
Set<String> keySet = hm.keySet();//返回所有键的集合
Iterator<String> key = keySet.iterator();
while(key.hasNext()){
String jian = key.next();//键
Integer zhi = hm.get(jian);//值
out.println("keySet..." + jian + "=" + zhi);
}
//entryset
Set<Map.Entry<String, Integer>> entrySet = hm.entrySet();//返回所有键值对的映射关系
Iterator<Map.Entry<String, Integer>> entry = entrySet.iterator();
while(entry.hasNext()){
Map.Entry<String, Integer> map = entry.next();
String jian = map.getKey();//键
Integer zhi = map.getValue();//值
out.println("entrySet..." + jian + "=" + zhi);
}
}
}

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