java map展开

最新推荐文章于 2022-12-15 16:46:32 发布

原创最新推荐文章于 2022-12-15 16:46:32 发布 · 463 阅读

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本文通过一个具体的Java代码示例介绍了如何使用三种不同的方法来遍历HashMap：1) 通过keySet获取所有的键，然后逐个取出对应的值；2) 通过entrySet获取所有的键值对，并分别处理键与值；3) 直接获取所有值进行遍历。这些方法对于理解HashMap的工作原理及其在实际应用中的使用非常有用。

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

public class Student2 {


	public static void main(String[] args) {
		// TODO Auto-generated method stub

		Map<String, Student> m = new HashMap<String, Student>();
		Student s1 = (new Student(18,"Lihua", "1"));
		Student s2 = (new Student(20, "xiaohong", "2"));
		Student s3 = (new Student(65, "xiaoMing", "3"));
		m.put("111", s1);
		m.put("222", s2);
		m.put("333", s3);
		
		//1
		Set<String> kk = m.keySet();
		Iterator<String> it = kk.iterator();
		while(it.hasNext())
		{
			String k1 = it.next();
			Student st = m.get(k1);
			System.out.println(st);
			
		}
		
		//2
		Set<Entry<String, Student>> en = m.entrySet();
		Iterator<Entry<String, Student>> it2 = en.iterator();
		while(it2.hasNext())
		{
			Entry<String, Student> ne = it2.next();
			Student value = ne.getValue();
			String key = ne.getKey();
			System.out.println(key);
			System.out.println(value);
			
		}
		
		//3
		Collection<Student> c = m.values();
		Iterator<Student> it3 = c.iterator();
		while(it3.hasNext())
		{
			Student next = it3.next();
			System.out.println(next);
		}
	}

}