java - 将 Arrays.sort 与 Lambda 结合使用

Question

我正在尝试学习并从 Java 7 切换到 Java 8。
虽然我在切换 Arrays.sort 时遇到问题，这给出了我的错误:类型不适用。
我知道有一些更好的方法可以完成相同的任务，但我想使用相同的函数来更好地理解。
提前致谢。

package src;

import java.util.Arrays;
import java.util.Comparator;

public class Java8Learning {
    public static void main(String[] args){
        Integer[] numbers = {4,5,3,2,6,1};
        -------java 7 ---------
        Arrays.sort(numbers, new Comparator<Integer>() {
            @Override
            public int compare(Integer firstNumber, Integer secondNumber){
                System.out.print("comparing :"+ firstNumber + " and " + secondNumber);
                return Integer.compare(firstNumber, secondNumber);
            }
        });
        -------java 8 ---------
        // it gave me error
        //The method sort(T[], Comparator<? super T>) in the type Arrays is not applicable for the arguments (Integer[], (<no type> firstNumber, <no type> secondNumber) -> {})
        Arrays.sort(numbers, (firstNumber, secondNumber) -> 
                                 {  System.out.print("comparing :"+ firstNumber + " and " + secondNumber);
                                     Integer.compare(firstNumber, secondNumber);
                                 });

    }
}

Answer 1

在 Integer.compare 之前错过了返回

Arrays.sort(numbers, (firstNumber, secondNumber) -> 
                     {  System.out.print("comparing :"+ firstNumber + " and " + secondNumber);
                        return Integer.compare(firstNumber, secondNumber);
                     });