import java.util.Arrays;
import java.util.*;
public class Lambda
{

public static void main(String[] args)
{
    String[] arr1 = new String[]{"java" , "fkava" , "fkit" , "ios" , "android"};    
    Arrays.parallelSort(arr1 , (o1 , o2) -> o1.length() - o2.length());
    System.out.println(Arrays.toString(arr1));
}

}

我没弄明白Arrays.parallelSort(arr1 , **)第二个参数的意思，尝试把Lambda表达式转换成匿名内部类，可一直编译出错。
下面是我改的代码

import java.util.Arrays;
import java.util.*;
public class Lambda
{

public static void main(String[] args)
{
    String[] arr1 = new String[]{"java" , "fkava" , "fkit" , "ios" , "android"};    
    Arrays.parallelSort(arr1, new Comparator()
    {    
         public int compare(String o1, String o2)
        {
             return o1.length() - o2.length();
        }
    }); 
    System.out.println(Arrays.toString(arr1));
}

}