java - 如何使用arraylist JAVA从矩阵中获取值

Question

我有这个矩阵:

A  B  C  D  E  
0  0  0  1  0 -> index 0 in arrList  
0  0  1  1  0 -> index 1 in arrList   
0  0  1  0  0 -> index 2 in arrList   
1  0  1  0  0 -> index 3 in arrList 

所以在ArrayList中arrList包含:[[0,0,0,1,0], [0,0,1,1,0], [0,0,1,0,0], [ 1,0,1,0,0]]

如何从JAVA中的arrList获取A、B、C、D、E列的值作为Example输出？

Example output:   
A: [0,0,0,1]  
B: [0,0,0,0]  
C: [0,1,1,1]  
D: [1,1,0,0]  
E: [0,0,0,0]

请帮忙。谢谢。

Answer 1

精美的 Java 8 解决方案

import java.util.List;
import java.util.stream.IntStream;

import static java.lang.System.lineSeparator;
import static java.util.Arrays.asList;
import static java.util.stream.Collectors.joining;

public class Example {
    public static void main(String[] args) {
        List<List<Integer>> matrix = asList(
                asList(0, 0, 0, 1),
                asList(0, 0, 0, 0),
                asList(0, 1, 1, 1),
                asList(1, 1, 0, 0),
                asList(0, 0, 0, 0)
        );
        System.out.println("Example output:");
        System.out.println(IntStream.range(0, matrix.size())
                .mapToObj(i -> (char) ('A' + i) + ": [" + matrix.get(i)
                        .stream()
                        .map(String::valueOf)
                        .collect(joining(", "))
                        + "]"
                )
                .collect(joining(lineSeparator())));
    }
}

输出

Example output:
A: [0, 0, 0, 1]
B: [0, 0, 0, 0]
C: [0, 1, 1, 1]
D: [1, 1, 0, 0]
E: [0, 0, 0, 0]

作为一个大单行因为为什么不

System.out.println(((Function<List<List<Integer>>, String>) (matrix -> "Example output: " + lineSeparator() + range(0, matrix.size()).mapToObj(i -> (char) ('A' + i) + ": [" + matrix.get(i).stream().map(String::valueOf).collect(joining(", ")) + "]").collect(joining(lineSeparator())))).apply(asList(asList(0, 0, 0, 1), asList(0, 0, 0, 0), asList(0, 1, 1, 1), asList(1, 1, 0, 0), asList(0, 0, 0, 0))));
// extra space for scroll