Java项目：学生管理系统（HashSet）

    package com.zzu.test;
    
    import java.util.HashSet;
    import java.util.Scanner;
    
    import com.zzu.vo.Student;
    
    public class Main {
      
    	private static HashSet<Student> set = new HashSet<Student>();
    	public static void main(String[] args) {
    		System.out.println("*********************************");
    		System.out.println("*\t\t\t\t*");
    		System.out.println("*\t欢迎使用学生信息管理系统\t*");
    		System.out.println("*\t\t\t\t*");
    		System.out.println("*********************************");
    		while (true) {
    			menu();
    		}
    	}
      
    	static void menu() {
    		System.out.println("1、添加学生信息");
    		System.out.println("2、删除学生信息");
    		System.out.println("3、修改学生信息");//地址传递
    		System.out.println("4、查询学生信息");//name
    		System.out.println("请输入操作，以Enter键结束:");
    		Scanner scanner = new Scanner(System.in);
    		int option  = scanner.nextInt();
    		switch (option) {
    			case 1:{
    				System.out.println("请输入学生id");
    				String id = scanner.next();
    				System.out.println("请输入学生name");
    				String name = scanner.next();
    				System.out.println("请输入学生mobile");
    				String mobile = scanner.next();
    				System.out.println("请输入学生address");
    				String address = scanner.next();
    				Student student = new Student();
    				student.setId(id);
    				if(set.contains(student)) {
    					System.out.println("该学生学号重复，请重新输入");
    					return ;
    				}
    				student.setName(name);
    				student.setMobile(mobile);
    				student.setAddress(address);
    				set.add(student);
    				System.out.println("添加成功");
    				System.out.println("*****"+set.size());
    				break;
    			}
    	       
    			case 2:{
    				Student student = new Student();
    				System.out.println("请输入学生id");
    				String id = scanner.next();
    				student.setId(id);
    				if(set.remove(student)) {//判断是否删除成功
    					System.out.println("删除成功");
    					return;
    				}
    				System.out.println("删除失败");
    				break;
    			}
    	        
    
    			case 3:{
    				Student student = new Student();
    				System.out.println("请输入学生id");
    				String id = scanner.next();
    				student.setId(id);
    				if(!set.contains(student)) {
    					System.out.println("学号为："+id+"的学生不存在！修改失败");
    					return;
    				}
    				for(Student stu : set) {//stu是需要修改学生的地址
    					if(stu.getId().equals(id)) {
    						System.out.println("请输入学生新name");
    						String name = scanner.next();
    						System.out.println("请输入学生新mobile");
    						String mobile = scanner.next();
    						System.out.println("请输入学生新address");
    						String address = scanner.next();
    						stu.setName(name);
    						stu.setMobile(mobile);
    						stu.setAddress(address);
    						System.out.println("修改成功");
    						return;
    					}
    				}
    				break;
    			}
    				
    			case 4:{
    				Student student = new Student();
    				System.out.println("请输入学生学号");
    				String id = scanner.next();
    				student.setId(id);
    				if(!set.contains(student)) {
    					System.out.println("我找到学号为："+id+"的学生！");
    					return ;
    				}
    				for(Student stu : set) {
    					if(stu.getId().equals(id)) {
    						System.out.println(stu);
    						return;
    					}
    				}
    				break;
    			}
    			default:
    				System.out.println("I'm Sorry,there is not the "+option+" option,please try again.");
    		}
    	}
    }
    
    
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
    

    package com.zzu.vo;
    
    public class Student {
    
    	private String id;
    	private String name;
    	private String mobile;
    	private String address;
    	public String getId() {
    		return id;
    	}
    	public void setId(String id) {
    		this.id = id;
    	}
    	public String getName() {
    		return name;
    	}
    	public void setName(String name) {
    		this.name = name;
    	}
    	public String getMobile() {
    		return mobile;
    	}
    	public void setMobile(String mobile) {
    		this.mobile = mobile;
    	}
    	public String getAddress() {
    		return address;
    	}
    	public void setAddress(String address) {
    		this.address = address;
    	}
    	
    	@Override
    	public int hashCode() {
    		// TODO Auto-generated method stub
    		return id.hashCode();
    	}
    	@Override//equals
    	public boolean equals(Object obj) {//this代表正在试图保存的对象；obj是HashSet集合中保存的数据
    		if(obj instanceof Student) {
    			Student stu = (Student)obj;
    			//return this.id.equals(stu.id);
    			return stu.id.equals(this.id);
    		}
    		return false;
    	}
    	
    	@Override
    	public String toString() {
    		return "Student [id=" + id + ", name=" + name + ", mobile=" + mobile + ", address=" + address + "]";
    	}
    }