如何实现字符串与整数混合输入的加法及值初始化功能？

Alright, let's get your code working properly for the required operations. First, let's break down the problems in your current code:

• You’re trying to call next() and nextLong() on a String variable s—that’s a mistake! Those methods belong to the Scanner class, not plain String objects.
• The "set" operation logic is completely missing: right now, when you get a "set" command, you just read the value but never update x with it.
• While the idea of tracking the maximum x value is there, the broken input handling means the core operations won’t run as intended.

Here’s the corrected, working version of your code that handles both commands correctly and tracks the highest value x reaches:

import java.util.Scanner;

public class Solution {
    static long maximumProgramValue(int n) {
        long x = 0L;
        long maxValue = 0L; // Renamed for clarity—this tracks the highest x we've seen
        
        Scanner scanner = new Scanner(System.in);
        for (int i = 0; i < n; i++) {
            // Read the operation first (either "add" or "set")
            String operation = scanner.next();
            // Then read the numeric value associated with the operation
            long value = scanner.nextLong();
            
            if (operation.equals("add")) {
                x += value; // Add the value to x
            } else if (operation.equals("set")) {
                x = value; // Set x directly to the provided value
            }
            
            // Update our max value if current x is larger than what we've recorded
            if (x > maxValue) {
                maxValue = x;
            }
        }
        scanner.close(); // Clean up the scanner resource
        return maxValue;
    }

    public static void main(String[] args) {
        Scanner inputScanner = new Scanner(System.in);
        int n = inputScanner.nextInt();
        inputScanner.nextLine(); // Consume the leftover newline after reading n
        
        long result = maximumProgramValue(n);
        System.out.println(result);
        
        inputScanner.close();
    }
}

What We Fixed & Why: #

• Proper Input Reading: We use the Scanner directly to pull the operation string and numeric value, which fixes the invalid method calls on a String.
• "set" Operation Logic: We added the code to set x to the input value when the command is "set"—that’s the core functionality you were missing.
• Clearer Variable Names: Renamed count to maxValue so anyone reading the code can immediately tell what it’s for.
• Cleaner Loop: Switched from a while loop to a for loop since we know exactly how many operations we need to process (n).
• Resource Cleanup: Added close() calls on the scanners to make sure we’re not leaving resources hanging.
• Main Method Fix: Handled the newline after reading n to prevent the first operation read from picking up an empty string.

Now this code will do exactly what you need:

• When you input add y, it adds y to the current value of x
• When you input set x, it resets x to the provided value
• It keeps track of the highest value x ever hits and returns that number at the end.

内容的提问来源于stack exchange，提问作者rs dwd