Map接口的遍历实现javaqq42108133的博客-

Map接口的四种遍历方式

1. 使用Set集合迭代器方法
   1）先使用keySet方法获取关键字集合的Set集合
   2）再根据Set集合的iterator方法得到相应的迭代器
   3）根据Set的迭代器进行遍历
   4）关键代码如下

方式一：迭代器while循环

System.out.println("==========遍历方式一==========");   Set keySet = map.keySet();   Iterator iterator = keySet.iterator();   while(iterator.hasNext()){    Object key = iterator.next();    System.out.println(key+"---"+map.get(key));   } 

方式二：增强for循环

System.out.println("==========遍历方式二==========");   for (Object key1 : keySet) {    System.out.println(key1+"---"+map.get(key1));   } 

2. 使用entrySet迭代器方法
   1）先使用Map接口的entrySet方法得到一个Set集合
   2）根据得到的Set集合得到新的iterator迭代器
   3）根据迭代器进行遍历

方式三

System.out.println("==========遍历方式三==========");   Set entrySet = map.entrySet();   Iterator iterator2 = entrySet.iterator();   while(iterator2.hasNext()){    Map.Entry node = (Map.Entry)iterator2.next();    System.out.println(node.getKey()+"---"+node.getValue());   } 

方式四

System.out.println("==========遍历方式四==========");   for (Object object : entrySet) {    Map.Entry node2 = (Map.Entry)object;    System.out.println(node2.getKey()+"---"+node2.getValue());   } 

3. 最后附上完整的代码

代码

package Test;  import java.util.HashMap; import java.util.Iterator; import java.util.Map; import java.util.Set;  public class MapForeach {  @SuppressWarnings({ "unchecked", "rawtypes" })  public static void main(String[] args) {   HashMap map = new HashMap();   Student student1 = new Student("001","汤小强");   Student student2 = new Student("002","汤大强");   Student student3 = new Student("003","汤很强");   Student student4 = new Student("004","汤最强");   map.put(student1.getID(), student1);   map.put(student2.getID(), student2);   map.put(student3.getID(), student3);   map.put(student4.getID(), student4);      System.out.println("==========遍历方式一==========");   Set keySet = map.keySet();   Iterator iterator = keySet.iterator();   while(iterator.hasNext()){    Object key = iterator.next();    System.out.println(key+"---"+map.get(key));   }         System.out.println("==========遍历方式二==========");   for (Object key1 : keySet) {    System.out.println(key1+"---"+map.get(key1));   }      System.out.println("==========遍历方式三==========");   Set entrySet = map.entrySet();   Iterator iterator2 = entrySet.iterator();   while(iterator2.hasNext()){    Map.Entry node = (Map.Entry)iterator2.next();    System.out.println(node.getKey()+"---"+node.getValue());   }      System.out.println("==========遍历方式四==========");   for (Object object : entrySet) {    Map.Entry node2 = (Map.Entry)object;    System.out.println(node2.getKey()+"---"+node2.getValue());   }  } }   class Student{  private String name;  private String ID;  public Student(String iD, String name ) {   super();   this.name = name;   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) {   ID = iD;  }  @Override  public String toString() {   // TODO Auto-generated method stub   return "ID ="+ID+" name="+name;  } }