List Sort Advanced

Initial code:

An Apple class

 Public classapple{String color;    Integer size;        Float weight;  PublicApple () {} PublicApple (String color, Integer size, Float weight) { This. color =color;  This. Size =size;  This. Weight =weight; }     PublicString GetColor () {returncolor; }     Public voidsetcolor (String color) { This. color =color; }     PublicInteger GetSize () {returnsize; }     Public voidsetSize (Integer size) { This. Size =size; }     PublicFloat getweight () {returnweight; }     Public voidsetweight (Float weight) { This. Weight =weight; } @Override PublicString toString () {return"apple{" + "weight=" + weight + ", size=" + size + ", color=" + Color + ‘}‘; }}

View Code

The main function is assigned a value of one print

     Public Static voidMain (string[] args) {List<Apple> applelist =NewArraylist<>(); Applelist.add (NewApple ("Red", 111, 333F)); Applelist.add (NewApple ("Yellow", 333, 222F)); Applelist.add (NewApple ("Blue", 222, 888F)); Applelist.add (NewApple ("Black", 555, 777F)); Applelist.add (NewApple ("Pink", 444, 111F)); Applelist.add (NewApple ("Green", 666, 444F)); }    Private Static<T>voidForEach (list<t>list) {         for(Object vo:list) {System.out.println (vo.tostring ()); }    }

First Level: Pass code

Apple class implements comparator replication compare

 Public class Implements Comparator<apple> {    String color;    Integer size;    Float weight;    @Override    publicint  Compare (Apple O1, Apple O2) {        return o1.getsize (). CompareTo (O2.getsize ());    }        ...}

        Applelist.sort (new  Apple ());        ForEach (applelist);

Printing results:

Second Level: Anonymous class

Apple class restore does not implement comparator

        Applelist.sort (new comparator<apple>() {            @Override            publicint Compare (Apple O1, Apple O2) {                return  o1.getsize (). CompareTo (O2.getsize ());            }        );        ForEach (applelist);

Print the same result

Level three: Using lambda expressions

The same way of passing code. Lightweight notation

        Applelist.sort (Apple o1,apple O2), o1.getsize (). CompareTo (O2.getsize ()));        ForEach (applelist);

Can you be a little more concise? Yes.

The Java compiler can infer the type of an expression parameter based on the context of the lambda, so you can omit the parameter type when writing a lambda

        Applelist.sort (O1,O2), o1.getsize (). CompareTo (O2.getsize ()));        ForEach (applelist);

Can you be a little more concise? Yes.

Comparator has a comparing static helper method that can accept a function to extract the comparable key value and generate a Comparator object

        Applelist.sort (Comparator.comparing ((a),a.getsize ()));        ForEach (applelist);

Level fourth: Using method references

        Applelist.sort (comparator.comparing (apple::getsize));        ForEach (applelist);

Method references are simply LAMPBDA syntax sugars that involve a single method, and are used in the same way as calling static methods in PHP, like: methods.

List Sort Advanced