如何为Java累加计算器添加循环直至用户输入退出指令？

Got it, let's tweak your code so it runs non-stop until you type "exit" or "e" to quit. Here's the revised version with clear explanations of the changes:

Revised Code #

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        System.out.println("Welcome to the persistent calculator!");
        System.out.println("Starting result: 0");
        System.out.println("Enter operations like '[operator] [number]' (e.g., - 7), or type 'exit'/'e' to close.");
        
        Scanner scanner = new Scanner(System.in);
        int currentResult = 0;
        
        // Loop indefinitely until exit command is received
        while (true) {
            System.out.print("> ");
            String input = scanner.nextLine().trim().toLowerCase();
            
            // Check if user wants to exit
            if (input.equals("exit") || input.equals("e")) {
                System.out.println("Closing calculator... See you!");
                break;
            }
            
            // Split input into operator and number components
            String[] inputParts = input.split("\\s+");
            if (inputParts.length != 2) {
                System.out.println("Oops, invalid input! Use format like '+ 10' or type 'exit' to quit.");
                continue;
            }
            
            String operator = inputParts[0];
            int rightOperand;
            try {
                rightOperand = Integer.parseInt(inputParts[1]);
            } catch (NumberFormatException e) {
                System.out.println("That's not a valid number! Please enter an integer.");
                continue;
            }
            
            // Calculate and update the result
            try {
                currentResult = compute(currentResult, operator, rightOperand);
                System.out.println("Current result: " + currentResult);
            } catch (IllegalArgumentException e) {
                System.out.println(e.getMessage());
            }
        }
        scanner.close();
    }

    private static int compute(int left, String op, int right) {
        // Note: Multiplication has potential issues, not addressed per requirement
        switch (op.charAt(0)) {
            case '+':
                return left + right;
            case '-':
                return left - right;
            case '*':
                return left * right;
            case '/':
                // Added division by zero check to avoid crashes
                if (right == 0) {
                    throw new IllegalArgumentException("Cannot divide by zero!");
                }
                return left / right;
            default:
                throw new IllegalArgumentException("Unknown operator: " + op);
        }
    }
}

Key Improvements Explained #

• Continuous Loop: Used a while(true) loop that runs forever until the user enters "exit" or "e"—this triggers a break to exit the loop and close the program.
• Better Input Handling: Reads full lines of input instead of using next()/nextInt() directly, which avoids errors when the user types an exit command instead of an operator/number pair.
• Error Resilience: Added checks for invalid input formats, non-integer values, unknown operators, and division by zero to make the calculator more user-friendly and crash-resistant.
• Persistent State: The currentResult variable keeps track of the last calculation result, which is automatically used as the left operand for every subsequent operation.
• Clear Prompts: Added simple instructions and prompts to guide users on how to interact with the tool.

Quick Note #

As requested, the multiplication logic is kept in its original state (with potential issues unaddressed).

内容的提问来源于stack exchange，提问作者Ichmag17