Java中的不同遍历方式

已知一个Person类：

 public class Person implements Comparable<Person>{
     String name;
     String id;
     public Person(String name,String id) {
         this.name=name;
         this.id=id;
     }

     public String getName() {
         return name;
     }

     public void setName(String name) {
         this.name = name;
     }

     public String getId() {
         return id;
     }

     public void setId(String id) {
         this.id = id;
     }

     public boolean equals(Object o) {
         if(!(o instanceof Person)) {
             return false;
         }
         Person person=(Person) o;
         return this.id.equals(person.id);
     }
     @Override
     public int compareTo(Person o) {
         if(o==null)
             return ;
         return this.id.compareTo(o.id);
     }    

     public String toString() {
         return String.format("%s-%s", name,id);
     }

     public int hasCode() {
         return id.hashCode();
     }
 }

1、遍历HashMap的不同方法：

 import java.util.HashMap;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.Set;

 import difficult.Person;
 public class HashMapDemo {
     public static void main(String[] args) {
         Map<String, Person> map=new HashMap<>();
         Person p1=new Person("张三", "");
         map.put(p1.getId(), p1);
         map.put("", new Person("", "李四"));
         map.put("", new Person("", "王五"));
         System.out.println(map);

         System.out.printf("%s-%s\n","",map.get(""));
         //增强型for，元素类型为Entry<String,Person>
         for(Entry<String, Person> entry:map.entrySet()) {
             System.out.printf("%s-%s ",entry.getKey(),entry.getValue());
         }
         System.out.println();
         //利用set来遍历
         Set<String> keys=map.keySet();
         for(String key:keys) {
             Person value=map.get(key);
             System.out.printf("%s-%s ",key,value);
         }
         System.out.println();
     }
 }

2、遍历list的不同方法

 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;

 import difficult.Person;

 public class IterateList {

     public static void main(String[] args) {
         List<Person> persons = new ArrayList<>();//，List为一个接口，定义一个泛型为Person的ArrayList表
         Person p = new Person("1001", "张三");

         persons.add(p);
         persons.add(p);
         persons.add(new Person("1002", "李四"));
         persons.add(new Person("1003", "王五"));
         persons.add(new Person("1004", "沈六"));

         //遍历1：下标
         int len=persons.size();
         for(int i=0;i<len;i++) {
             Person person=persons.get(i);
             System.out.print(person+"\t");
         }
         System.out.println();
         //遍历2：迭代器
         Iterator<Person> iterator=persons.iterator();
         while(iterator.hasNext()) {
             Person person=iterator.next();
             System.out.print(person+"\t");
         }
         System.out.println();

         //遍历3：增强型for
         for(Person person:persons) {
             System.out.print(person+"\t");
         }
         System.out.println();

         int[] data= {1,3,5,7,9};
         for(int dat:data) {
             System.out.print(dat+"\t");
         }
     }
 }

3、利用向量（通过枚举）遍历list

 import java.util.ArrayList;
 import java.util.Enumeration;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Vector;

 import difficult.Person;

 public class VectorAndList {

     public static void main(String[] args) {
         List<Person> persons = new ArrayList<>();
         Person p = new Person("1001", "张三");

         persons.add(p);
         persons.add(p);
         persons.add(new Person("1002", "李四"));
         persons.add(new Person("1003", "王五"));
         persons.add(new Person("1004", "沈六"));

         // 遍历二：迭代器
         Iterator<Person> iterator=persons.iterator();
         while(iterator.hasNext()) {
             Person person=iterator.next();
             System.out.print(person+"\t");
         }
         System.out.println();

         //向量
         Vector<Person> vector=new Vector<>();
         vector.addAll(persons);
         //通过枚举遍历
         Enumeration<Person> enu=vector.elements();
         while(enu.hasMoreElements()) {
             Person person=enu.nextElement();
             System.out.print(person+"\t");
         }
         System.out.println();

     }
 }