java复习总结3

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     （key值不可重复）

 案例：
       package hpu.edu.cn.Admin;

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

public class MapTest {

	/**
	 * @param args
	 */
	public Map<String, Student> students;
	public MapTest(){
		this.students = new HashMap<String,Student>();
	}
	public void testPut(){
		Scanner console = new Scanner(System.in);
		int i = 0;
		while(i < 3){
			System.out.println("请输入学生ID：");
			String ID = console.next();
			Student st = students.get(ID);
			if(st == null){
				System.out.println("请输入学生姓名：");
				String name = console.next();
				Student newSt = new Student(ID,name);
			    students.put(ID, newSt);
			    System.out.println("成功添加学生：" + students.get(ID).name);
			    i++;
			}else{
				System.out.println("该学生ID已被占用！！");
				continue;
			}
			
		}
	}
	public void testKeySet(){
		Set<String> keySet = students.keySet();
		System.out.println("总共有：" + students.size() + "个学生！！");
		
		for (String stuId:keySet) {
			Student st = students.get(stuId);
			if(st != null){
				System.out.println("学生：" + st.name);
			}
		}
	}
	public void testRemove(){
		Scanner console = new Scanner(System.in);
		while(true){
			System.out.println("请输入要删除学生的ID：");
			String ID = console.next();
			Student st = students.get(ID);
			if(st == null){
				System.out.println("该ID不存在！！");
				continue;
			}
			students.remove(ID);
			System.out.println("成功删除学生：" + st.name);
			break;
		}
	}
	/*
	 * 
	 * entrySet方法来遍历Map
	 **/
	public void testEntrySet(){
		Set<Entry<String,Student>> entrySet = students.entrySet();
		for(Entry<String,Student> entry:entrySet){
			System.out.println("取得键：" + entry.getKey());
			System.out.println("对应的值为：" + entry.getValue().name);
			
		}
	}
	public void testModify(){
		System.out.println("请输入要修改的学生ID：");
		Scanner console = new Scanner(System.in);
		while(true){
			String stuID = console.next();
			Student student = students.get(stuID);
			if(student == null){
				System.out.println("该ID不存在！请重新输入！");
				continue;
			}
			
			System.out.println("当前该学生ID，所对应的学生为：" + student.name);
			System.out.println("请输入新的学生姓名：");
			String name = console.next();
			Student newSt = new Student(stuID,name);
			students.put(stuID,newSt);
			System.out.println("修改成功！！");
			break;
		}
	}
	public static void main(String[] args) {
		// TODO Auto-generated method stub
        MapTest mt = new MapTest();
        mt.testPut();
        mt.testKeySet();
	 mt.testRemove();
        mt.testEntrySet();
	}

}

java复习总结3

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原文地址：http://blog.csdn.net/wojiaohuangyu/article/details/50855890