Java二维数组列最大值提取程序遇数组越界问题求助

Hey there! Let's work through fixing your ArrayIndexOutOfBoundsException and getting your program to correctly extract the maximum value from each column of your 2D array.

原代码的核心问题 #

Let's break down why you're hitting that error and where the logic is off:

• 二维数组维度搞反了: You declared int[][] table = new int [col][row]; but then tried to access table[j][i] where j runs up to row-1. If row is larger than col, this will immediately cause an out-of-bounds error—since your array only has col rows, you can't access rows beyond that.
• 最大值存储数组定义错误: Your t array is sized for row elements, but you need to store one maximum per column (so it should be sized for col elements instead).
• 最大值赋值逻辑混乱: You're incrementing m and assigning to t[m] every time you find a larger value, which would fill t with multiple values per column instead of just the final maximum for each column.

修正后的代码 #

import java.util.Arrays;
import java.util.Scanner;

public class ColumnMaxExtractor {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        
        // 先输入行数和列数，明确顺序避免维度混淆
        System.out.println("请输入行数:");
        int row = sc.nextInt();
        System.out.println("请输入列数:");
        int col = sc.nextInt();
        
        // 正确定义二维数组：行数为row，每行包含col个元素
        int[][] table = new int[row][col];
        // 结果数组长度等于列数，用来存每列的最大值
        int[] columnMaxes = new int[col];
        
        // 填充二维数组
        System.out.println("请输入数组元素（按行依次输入）:");
        for (int i = 0; i < row; i++) {
            for (int j = 0; j < col; j++) {
                table[i][j] = sc.nextInt();
            }
        }
        
        // 遍历每一列，查找最大值
        for (int i = 0; i < col; i++) {
            // 初始化当前列的最大值为该列第一行的元素
            int max = table[0][i];
            // 遍历当前列的所有行，更新最大值
            for (int j = 1; j < row; j++) {
                if (table[j][i] > max) {
                    max = table[j][i];
                }
            }
            // 将当前列的最大值存入结果数组
            columnMaxes[i] = max;
        }
        
        // 输出最终结果
        System.out.println("每列的最大值为:");
        System.out.println(Arrays.toString(columnMaxes));
        sc.close();
    }
}

关键修正点说明 #

• 数组维度对齐: We now define table as new int[row][col], matching the input order of rows first, then columns. This ensures we never try to access a row or column that doesn't exist in the array.
• 结果数组大小匹配: columnMaxes is sized to col elements, which exactly matches the number of columns we need to process.
• 清晰的最大值查找逻辑: For each column, we start with the first element as the initial max, then iterate through all remaining rows in that column to update the max if a larger value is found. Finally, we store that single, final maximum in the results array.

示例运行效果 #

If you input:

3
2
1 5
3 2
4 7

The output will be:

每列的最大值为:
[4, 7]

内容的提问来源于stack exchange，提问作者user12741421