jdk8_lambda expression

1. Background:

package com.zhangwl.pg0922.pg02_Jdk8.Lambda.pkg01;

import java.util.Comparator;

/**
 * @ClassName LengthComparator
 * @Description 定制一个比较器用于排序
 * @Author zhangwl
 * @Date 2019/9/22 21:53
 * @Version 1.0
 **/
public class LengthComparator implements Comparator<String> {

    @Override
    public int compare(String o1, String o2) {
        return o1.length() - o2.length();
    }
}

com.zhangwl.pg0922.pg02_Jdk8.Lambda.pkg01 Package; 

Import java.util.Arrays; 

/ ** 
* @ClassName RunMain 
* @Description 
* @author zhangwl 
* @date 2019/9/22 22:06 
* @Version 1.0 
* * / 
public class RunMain { 
    public static void main (string [] args) { 
        / * define an array of strings for comparison * / 
        string [] = strArr new new string [] { "BCC", "AC", "CAAD "," B "}; 
        System.out.println (" before sorted array of strings: "+ Arrays.asList (strArr)); 
        / * a comparator for comparing a custom ordering element * / 
        lengthComparator lengthComparator new new lengthComparator = () ; 
        Arrays.sort (strArr, lengthComparator); 
        "array of strings after sorting:" System.out.println (+ arrays.asList(strArr));
    }
} 

The result:

Before sorted string array: [bcc, ac, caad, b]
array of strings after sorting: [b, ac, bcc, caad]

 Before jdk8, java not directly transmit a transmission code segment or a segment of code is not easy, java language is an object-oriented, it is necessary to construct an object, a method must be included in the class of this object, the method It can contain code segments needed; so was born Lambda expressions.

 Lambda expressions, in fact, must be passed a variable code segment and code specifications, for example: (String a, String b) -> {a + b}. Lambda expressions with expressions is a parameter which indicates that an anonymous inner class. 

2, case presentations:

com.zhangwl.pg0922.pg02_Jdk8.Lambda.pkg02 Package; 

Import java.util.Arrays; 

/ ** 
* @ClassName LambdaRunMain 
* @Description Lambda expression using a custom comparator purpose sorted string array 
* @Author zhangwl 
@date 2019/9/22 23:41 * 
* @Version 1.0 
** / 
public class LambdaRunMain { 

    public static void main (String [] args) { 

        String [] = strArr new new String [] { "BCC", "AC" , "CAAD", "B"}; 
        System.out.println ( "before sorted array of strings:" + Arrays.asList (strArr)); 
        Arrays.sort (strArr, (First, SECOND) -> { 
            return First .length () - second.length (); 
        }); 
        System.out.println ( "after sorted array of strings:" + Arrays.asList (strArr)) ;
    }
}

operation result:

Before sorted string array: [bcc, ac, caad, b]
array of strings after sorting: [b, ac, bcc, caad]