자바8,람다식,객체정렬,Collections.sort,Lambda,Double Colon,Comparable, compare

자바8,람다식,객체정렬,Collections.sort,Lambda,Double Colon,Comparable, compare

아래 예제를 보시면 이해 되실 겁니다.

감사합니다.

package onj;

import java.util.ArrayList;

import java.util.Collections;

import java.util.List;

class OracleJavaCommunity {

private String name;

private int age;

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public int getAge() {

return age;

}

public void setAge(int age) {

this.age = age;

}

public String toString() {

return "[name : " + name + ", age=" + age + " ]";

}

}

//이름으로 정렬

class OjcSortByName  {

public int compare(OracleJavaCommunity ojc1, OracleJavaCommunity ojc2) {

return ojc1.getName().compareTo(ojc2.getName());

}

}

//나이로 정렬

class OjcSortByAge  {

public int compare(OracleJavaCommunity ojc1, OracleJavaCommunity ojc2) {

return ojc1.getAge() - ojc2.getAge();

}

}

public class LambdaTest2 {

public static void main(String[] args) {

OracleJavaCommunity ojc1 = new OracleJavaCommunity();

OracleJavaCommunity ojc2 = new OracleJavaCommunity();

OracleJavaCommunity ojc3 = new OracleJavaCommunity();

ojc1.setName("오라클");

ojc1.setAge(15);

ojc2.setName("자바");

ojc2.setAge(9);

ojc3.setName("닷넷");

ojc3.setAge(8);

List ojcs = new ArrayList();

ojcs.add(ojc1);

ojcs.add(ojc2);

ojcs.add(ojc3);

// 원본 출력, double colon 연산자이용

ojcs.forEach(System.out::println);

System.out.println("---------------------");

// age로 정렬1

Collections.sort(ojcs, (OracleJavaCommunity ojc4,

OracleJavaCommunity ojc5) -> {

return ojc4.getAge() - ojc5.getAge();

});

//정렬후 출력1

ojcs.forEach(System.out::println);

//이름(name)으로 정렬2

OjcSortByName sortOjc = new OjcSortByName();

Collections.sort(ojcs, 

(OracleJavaCommunity ojc6, OracleJavaCommunity ojc7) 

-> sortOjc.compare(ojc6,  ojc7));

//이름정렬후 출력2

System.out.println("---------------------");

ojcs.forEach(System.out::println);

//나이(age)로 정렬3

OjcSortByAge sortOjc2 = new OjcSortByAge();

Collections.sort(ojcs, sortOjc2::compare);

//나이정렬후 출력3

System.out.println("---------------------");

ojcs.forEach(System.out::println);

}

}

[결과]

[name : 오라클, age=15 ]

[name : 자바, age=9 ]

[name : 닷넷, age=8 ]

---------------------

[name : 닷넷, age=8 ]

[name : 자바, age=9 ]

[name : 오라클, age=15 ]

---------------------

[name : 닷넷, age=8 ]

[name : 오라클, age=15 ]

[name : 자바, age=9 ]

---------------------

[name : 닷넷, age=8 ]

[name : 자바, age=9 ]

[name : 오라클, age=15 ]