Map遍历方式

悠悠 2021-09-17 00:38 496阅读 0赞

map的三种遍历方法 写道

//集合的一个很重要的操作---遍历，学习了三种遍历方法，三种方法各有优缺点  
  
/\*  
\* To change this template, choose Tools | Templates  
\* and open the template in the editor.  
\*/  
package cn.tsp2c.liubao;  
  
import java.util.Collection;  
import java.util.HashMap;  
import java.util.Iterator;  
import java.util.Map;  
import java.util.Set;  
import java.util.TreeMap;  
  
/\*\*  
\*  
\* @author Administrator  
\*/  
public class TestMap \{  
  
public static void main(String\[\] args) \{  
Map<String, Student> map = new HashMap<String, Student>();  
Student s1 = new Student("宋江", "1001", 38);  
Student s2 = new Student("卢俊义", "1002", 35);  
Student s3 = new Student("吴用", "1003", 34);  
  
map.put("1001", s1);  
map.put("1002", s2);  
map.put("1003", s3);  
  
Map<String, Student> subMap = new HashMap<String, Student>();  
subMap.put("1008", new Student("tom", "1008", 12));  
subMap.put("1009", new Student("jerry", "1009", 10));  
map.putAll(subMap);  
  
work(map);  
workByKeySet(map);  
workByEntry(map);  
\}  
  
　　//最常规的一种遍历方法，最常规就是最常用的，虽然不复杂，但很重要，这是我们最熟悉的，就不多说了！！  
  
public static void work(Map<String, Student> map) \{  
Collection<Student> c = map.values();  
Iterator it = c.iterator();  
for (; it.hasNext();) \{  
System.out.println(it.next());  
\}  
\}  
  
　　//利用keyset进行遍历，它的优点在于可以根据你所想要的key值得到你想要的 values，更具灵活性！！  
  
public static void workByKeySet(Map<String, Student> map) \{  
Set<String> key = map.keySet();  
for (Iterator it = key.iterator(); it.hasNext();) \{  
String s = (String) it.next();  
System.out.println(map.get(s));  
\}  
\}  
  
　　//比较复杂的一种遍历在这里，呵呵~~他很暴力哦，它的灵活性太强了，想得到什么就能得到什么~~  
  
public static void workByEntry(Map<String, Student> map) \{  
Set<Map.Entry<String, Student>> set = map.entrySet();  
for (Iterator<Map.Entry<String, Student>> it = set.iterator(); it.hasNext();) \{  
Map.Entry<String, Student> entry = (Map.Entry<String, Student>) it.next();  
System.out.println(entry.getKey() + "--->" + entry.getValue());  
\}  
\}  
\}  
  
class Student \{  
  
private String name;  
private String id;  
private int age;  
  
public Student(String name, String id, int age) \{  
this.name = name;  
this.id = id;  
this.age = age;  
\}  
  
@Override  
public String toString() \{  
return "Student\{" + "name=" + name + "id=" + id + "age=" + age + '\}';  
\}  
\}