Javaで学生管理システムを書く(学生情報の追加、削除、修正、照会)

package keeper;

public class Student {

	//Java  
	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 String toString() {
		return "Student [id=" + id + ", name=" + name + ", mobile=" + mobile + ", address=" + address + "]";
	}
	
	
	
}

package keeper;

import java.util.Scanner;

public class Main {

	static int index = 0;	//  main()   static，      static，         
	static Student [] students = new Student[45]; 
	
	public static void main(String[] args) { 
		
		System.out.println("***********************************");
		System.out.println("*                        *");
		System.out.println("***********************************");
		
		for(;;) {	//   
			information();
		}
		
	}
	
	public static void information() {
		System.out.println("1、      ");
		System.out.println("2、      ");
		System.out.println("3、      ");
		System.out.println("4、      ");
		
		System.out.println("      ，  enter ");
		Scanner scanner = new Scanner(System.in);
		int option = scanner.nextInt();
		
		switch (option) {
			case 1:{
				if(index>students.length-1) {	//      
					System.out.println("    ");
					return;
				}
				System.out.println("·      ：");
				Student student = new Student();
				System.out.println("     ，  enter ： ");
				String id = scanner.next();
				student.setId(id);
				if(index>0) {
					for (Student stu : students) {
						if(stu == null) {	//      null ，       null,      
							break;
						}
						if(stu.getId().equals(student.getId())) {//        
							System.out.println("      ，       ：");
							student.setId(scanner.next());
							break;
						}
					}
				}
				System.out.println("     ，  enter ");
				student.setName(scanner.next());
				System.out.println("      ，  enter ");
				student.setMobile(scanner.next());
				System.out.println("       ，  enter ");
				student.setAddress(scanner.next());
				
				students[index] = student;	//             
				index++;
				System.out.println("    ");
				break;
			}
			case 2:{
				System.out.println("·      ");
				System.out.println("           ：");
				String id = scanner.next();
				
				index=0;
				for(Student student:students) {
					if(student == null) {
						break;
					}
					if(student.getId().equals(id)) { //         
						while(index<students.length-1) {
							students[index] = students[index+1]; //                  
							index++;
						}
						students[students.length-1] = null; //            ，        null；     ，       ，               
						System.out.println("    ，   ！");
						return;
					}
					index++;
				}
				
				System.out.println("      "+id+"   ，    ");
				return;
			}
			case 3:{			
				System.out.println("·      ");
				System.out.println("            ：");
				String id = scanner.next();
				
				for(Student student:students) {
					if(student == null) {
						break;
					}
					if(student.getId().equals(id)) {
						System.out.println("       ，  enter ");
						student.setName(scanner.next());
						System.out.println("        ，  enter ");
						student.setMobile(scanner.next());
						System.out.println("         ，  enter ");
						student.setAddress(scanner.next());
						System.out.println("    ，   ！");
						return;
					}
				}
				
				System.out.println("      "+id+"   ，    ！");
				return;
			}
			case 4:{
				
				boolean flag = false;
				System.out.println("·      ");
				System.out.println("           ：");
				String name = scanner.next();
				
				for(Student student: students) {
					if(student == null) {
						break;
					}
					if(student.getName().equals(name)) {
						System.out.println(student);
						flag = true;
					}
				}
				
				if(!flag) {
					System.out.println("   "+name+"      ");
					return;
				}		
				break;
			}
			default:
				System.out.println("     "+option+"   ");
		}
		
	}

}