java - 我必须创建一个 deepArray2String 方法，该方法需要一个 2D int 数组 'x' 并返回其字符串表示形式

Question

创建一个 deepArray2String 方法，该方法需要一个 2D int 数组 'a1' 并返回其字符串表示形式，可以将其写入控制台。

我已经尝试了一些逻辑，但我收到了这个错误:

tester.java:18: 错误:类型不兼容:StringBuffer 无法转换为 String 返回结果； ^

public String deepArray2String(int[][] a1){

    StringBuffer result = new StringBuffer();
    for (int i = 0; i < a1.length; i++) {
        for (int j = 0; j < a1[i].length; j++) {
            result.append("[" + a1[i][j] + "]");
            if (j == a1.length && i != a1.length-1) {
                result.append(",");
            }
        }
    }
    return result;
}

System.out.println (deepArray2String (new int [] [] {{1}, {2}, {4}}));

输出应该是 [1], [2], [4]]

System.out.println (deepArray2String (new int [] [] {{1}, {2, 3}}));

输出应该是 [[1], [2, 3]]

System.out.println (deepArray2String (new int [] [] {}));

输出应该是[]

System.out.println (deepArray2String (new int [] [] {{5, 3}, {1}, {-1, 1}}));

输出应该是 [[5, 3], [1], [-1, 1]]

Answer 1

无需重新发明轮子，Java在java.util.Arrays中已经有了内置的静态方法这样做。 Autoboxing意味着它将适用于任何原始类型的数组。

import java.util.Arrays;
import org.junit.Test;
import lombok.extern.slf4j.Slf4j;

@Slf4j
public class ExampleTest {

    @Test
    public void test() {
        log.info(Arrays.deepToString(new int[][] { { 1 }, { 2 }, { 4 } }));    
        log.info(Arrays.deepToString(new int[][] { { 1 }, { 2, 3 } }));    
        log.info(Arrays.deepToString(new int[][] {}));
        log.info(Arrays.deepToString(new int[][] { { 5, 3 }, { 1 }, { -1, 1 } }));
    }
}

结果

[main] INFO coaching.arrays.ExampleTest - [[1], [2], [4]]
[main] INFO coaching.arrays.ExampleTest - [[1], [2, 3]]
[main] INFO coaching.arrays.ExampleTest - []
[main] INFO coaching.arrays.ExampleTest - [[5, 3], [1], [-1, 1]]

参数的工作方式完全相同。

@Test
public void test() {
    int[][] a = new int[][] { { 1 }, { 2 }, { 4 } };
    log.info(Arrays.deepToString(a));

    int[][] a2 = new int[][] { { 1 }, { 2, 3 } };
    log.info(Arrays.deepToString(a2));

    int[][] a3 = new int[][] {};
    log.info(Arrays.deepToString(a3));

    int[][] a4 = new int[][] { { 5, 3 }, { 1 }, { -1, 1 } };
    log.info(Arrays.deepToString(a4));
}