java（集合遍历）

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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 CollectionTest {public static void main(String[] args) {//ArrayList遍历ArrayList<Object> arrayList= new ArrayList<Object>();arrayList.add("123");arrayList.add(456);arrayList.add(true);arrayList.add('a');System.out.println(arrayList);//打印结果：[123, 456, true, a]//方式一for (Object object : arrayList) {System.out.println(object);}//打印结果：123// 456//true//a//方式二for (int i = 0; i < arrayList.size(); i++) {System.out.println(arrayList.get(i));}//方式三Iterator<Object> iterator=arrayList.iterator();while(iterator.hasNext()){System.out.println(iterator.next());}//方式四for (int i = 0; i < arrayList.size(); i++) {System.out.println(arrayList.get(i));}//set集合无序的、不可重复的Set<Object> set = new HashSet<>();set.add("abc");set.add("666");set.add(777);//set.add(666);System.out.println(set);for (Object object : set) {System.out.println(object);}//打印结果：123// 456//true//a//方式二Iterator<Object> iterator=set.iterator();while(iterator.hasNext()){System.out.println(iterator.next());}//Map 无序的Person p1=new Person(11, "zhangsan");Person p2=new Person(11, "lisi");Map<String, Person> map =new HashMap<String, Person>();map.put(p1.name, p1);map.put(p2.name, p2);//System.out.println(map);Set<String> set1= map.keySet();Iterator<String> iterator1=set1.iterator();while(iterator1.hasNext()){System.out.println(map.get(iterator1.next()));}}} class Person{  int age ; String name ;public Person(int age, String name) {super();this.age = age;this.name = name;}@Overridepublic int hashCode() {final int prime = 31;int result = 1;result = prime * result + age;result = prime * result + ((name == null) ? 0 : name.hashCode());return result;}@Overridepublic boolean equals(Object obj) {if (this == obj)return true;if (obj == null)return false;if (getClass() != obj.getClass())return false;Person other = (Person) obj;if (age != other.age)return false;if (name == null) {if (other.name != null)return false;} else if (!name.equals(other.name))return false;return true;}@Overridepublic String toString() {return "Person [age=" + age + ", name=" + name + "]";}  }
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