自分で家計簿を書きます。

第一歩はまず需要を分析して何かの変数int balance=10000が必要です。        String details=「収支\t口座金額\t収支金額」tは 明「+」「        bollan loopFlags=true;先に枠を書いて循環で選択枠を印刷し、キーボードから選択項目を入力して終了するには、対応するメカニズムが必要です。

package com.xatu.edu;

public class shouzhi {

	public static void main(String[] args) {
		//       ，10000
		//            
		//             
		//     
		// 1     
		// 2         

		int balance = 10000;
		String details = "   \t     \t     \t    "+"
";
		boolean loopFlag = true;
		while (loopFlag) {
			System.out.println("-----------------        -----------------");
			System.out.println("   1        ");
			System.out.println("    2         ");
			System.out.println("3     ");
			System.out.println("4       ");
			System.out.println("    (1-4)：");
			char userInput = Utility.readMenuSelection();
			switch (userInput) {
			case '1':
				System.out.println(details);
				break;
			case '2':
				System.out.println("    ");
				int money = Utility.readNumber();
				System.out.println("      ");
				String info = Utility.readString();
				balance=balance+money;
				String 	str ="  \t"+balance+"\t"+money+"\t"+info+"
";
				details +=str;
				break;
			case '3':

				break;
			case '4':
				System.out.println("    ,");
				char confirm = Utility.readConfirmSelection();
				if(confirm=='Y') {
				loopFlag = false;}
				break;

			default:
				break;
			}

		}

	}

}

package com.xatu.edu;

import java.util.*;

public class Utility {
    private static Scanner scanner = new Scanner(System.in);
    
	public static char readMenuSelection() {
        char c;
        for (; ; ) {
            String str = readKeyBoard(1);
            c = str.charAt(0);
            if (c != '1' && c != '2' && c != '3' && c != '4') {
                System.out.print("    ，     ：");
            } else break;
        }
        return c;
    }

    public static int readNumber() {
        int n;
        for (; ; ) {
            String str = readKeyBoard(4);
            try {
                n = Integer.parseInt(str);
                break;
            } catch (NumberFormatException e) {
                System.out.print("      ，     ：");
            }
        }
        return n;
    }

    public static String readString() {
        String str = readKeyBoard(8);
        return str;
    }

    public static char readConfirmSelection() {
        char c;
        for (; ; ) {
            String str = readKeyBoard(1).toUpperCase();
            c = str.charAt(0);
            if (c == 'Y' || c == 'N') {
                break;
            } else {
                System.out.print("    ，     ：");
            }
        }
        return c;
    }

    private static String readKeyBoard(int limit) {
        String line = "";

        while (scanner.hasNext()) {
            line = scanner.nextLine();
            if (line.length() < 1 || line.length() > limit) {
                System.out.print("    （   " + limit + "）  ，     ：");
                continue;
            }
            break;
        }

        return line;
    }
}