简单的成绩管理系统（控制台操作）

要写一个管理系统，首先，我们需要明确该系统拥有的操作都是什么。如我们最常见的增删改查。

增加数据：

public class AddData {
	public static Scanner scanner = new Scanner(System.in);

	// 班级
	private String grade;
	// 学号
	private String id;
	// 姓名
	private String name;
	// 高数
	private String math;
	// 英语
	private String english;
	// Java
	private String java;
	// 物理
	private String physics;
	// 平均
	private double average;

	public void addData() throws IOException {
		BufferedReader br = new BufferedReader(new FileReader("D:\实训\data.txt"));
		try {
			String ided;
			// 学号
			System.out.println("学号");
			id = scanner.next();
			while ((ided = br.readLine()) != null) {

				String[] s = ided.split(" ");
				if (id.equals(s[1])) {
					System.out.println("该学号已存在，请确认后输入！");
					return;
				}
			}
			// 年级
			System.out.println("年级");
			grade = scanner.next();
			// 姓名
			System.out.println("姓名");
			name = scanner.next();
			// 数学
			System.out.println("数学");
			math = scanner.next();
			// 英语
			System.out.println("英语");
			english = scanner.next();
			// Java
			System.out.println("Java");
			java = scanner.next();
			// 物理
			System.out.println("物理");
			physics = scanner.next();

			average = (Double.parseDouble(math) + Double.parseDouble(english) + Double.parseDouble(java)
					+ Double.parseDouble(physics)) / 4;

			String o = "学号： " + id + " ,年纪： " + grade + " ,姓名： " + name + " ,数学： " + math + " ,英语： " + english
					+ " ,Java： " + java + " ,物理： " + physics + " ,平均： " + average;

			BufferedWriter bw = new BufferedWriter(new FileWriter("D:\实训\data.txt", true));
			bw.write(o);
			bw.newLine();
			bw.flush();
			bw.close();
			System.out.println("录入成功！");
		} catch (Exception e) {

		}
	}

删除数据：

public class DeleteData {
	public void deleteData() throws IOException{
		BufferedReader br = new BufferedReader(new FileReader("D:\实训\data.txt"));
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		System.out.println("请输入你要删除的学号:");
		String id = in.readLine();
		String a = "";
		String a1;
		String a2 = "";
		int ifExist = 0;
		
		while((a1 = br.readLine()) != null) {
			String[] s = a1.split(" ");
			a2 = a2+s[1]+" ";
			if(id.equals(s[1])) {
				System.out.println("删除成功！");
				continue;
			}
				else {
				BufferedWriter bw = new BufferedWriter(new FileWriter("D:\实训\data.txt"));
				bw.close();
				BufferedWriter bw1 = new BufferedWriter(new FileWriter("D:\实训\data.txt",true));
				a += a1 +"n";
				bw1.write(a);
				bw1.close();
			}
		}
		
		String[] s1 = a2.split(" ");
		for(int i = 0;i 
改变数据：
 
public class ChangeData {
	public static Scanner scanner = new Scanner(System.in);

	// 班级
	private String grade;
	// 姓名
	private String name;
	// 高数
	private String math;
	// 英语
	private String english;
	// Java
	private String java;
	// 物理
	private String physics;
	// 平均
	private double average;
	
public void changeData() throws IOException{
	BufferedReader br = new BufferedReader(new FileReader("D:\实训\data.txt"));
	BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
	System.out.println("请输入你要修改的学号：");
	String id = in.readLine();
	String a = "";
	String a1;
	String a2 = "";
	int ifExist = 0;
	
	try {
	while((a1 = br.readLine()) != null) {
		if(a1 == null || "".equals(a1)) {
			break;
		}
		String[] s = a1.split(" ");
		a2 += a2+a1+" ";
		if(id.equals(s[1])) {
			// 年纪
			System.out.println("年纪");
			grade = scanner.next();
			// 姓名
			System.out.println("姓名");
			name = scanner.next();
			// 数学
			System.out.println("数学");
			math = scanner.next();
			// 英语
			System.out.println("英语");
			english = scanner.next();
			// Java
			System.out.println("Java");
			java = scanner.next();
			// 物理
			System.out.println("物理");
			physics = scanner.next();

			average = (Double.parseDouble(math) + Double.parseDouble(english) + Double.parseDouble(java)
					+ Double.parseDouble(physics)) / 4;

			a += "学号： " + id + " ,年纪： " + grade + " ,姓名： " + name + " ,数学： " + math + " ,英语： " + english + " ,Java： " + java
					+ " ,物理： " + physics + ",平均： " + average+"n";
	
			System.out.println("修改成功！");
		}else {
			BufferedWriter bw = new BufferedWriter(new FileWriter("D:\实训\data.txt"));
			bw.close();
			BufferedWriter bw1 = new BufferedWriter(new FileWriter("D:\实训\data.txt",true));
			a += a1+"n";
			bw1.write(a);
			bw1.close();
			
		}
			BufferedWriter bw = new BufferedWriter(new FileWriter("D:\实训\data.txt"));
			bw.close();
			BufferedWriter bw1 = new BufferedWriter(new FileWriter("D:\实训\data.txt",true));
			bw1.write(a);
			bw1.close();
	}
	br.close();
	String[] s1 = a2.split(" ");
	for(int i = 0;i 
查找数据：
 
public class AllData {
public void ShowAll() throws IOException{
	String thisLine;
	BufferedReader br = new BufferedReader(new FileReader("D:\实训\data.txt"));
	File file = new File("D:\实训\data.txt");
    if (null == file || 0 == file.length() || !file.exists()) {
        System.out.println("当前没有数据，请录入数据后查看！");
    }else {
	while((thisLine = br.readLine()) != null) {
		System.out.println(thisLine);
	}
  }
	br.close();
}