集合排序 Comparator和Comparable的使用区别

Java 排序 Compare 

 

• Comparator接口
• Comparable接口
• 区别

 

在Java中使用集合来存储数据时非常常见的,集合排序功能也是常用功能之一.下面看一下如何进行集合排序,常用的方法有: Comparator和Comparable

Comparator接口

使用步骤:

1. 新建比较类,
2. 实现Comparator接口,
3. 重写compare方法,

1. package sort; 

   ---

2.  

   ---

3. import java.util.Comparator; 

   ---

4.  

   ---

5. public class LuckBoyCompare implements Comparator<LuckBoy>{ 

   ---

6.  

   ---

7. @Override 

   ---

8. public int compare(LuckBoy o1, LuckBoy o2) { 

   ---

9. return o1.getAge()-o2.getAge(); 

   ---

10. } 

    ---

11.  

    ---

12. } 

    ---

13.  

    ---

• 调用Collections.sort()方法进行排序,
• 形式:Collections.sort(集合, 比较器实例).

1. @Test 

   ---

2. public void test1() { 

   ---

3. List<LuckBoy> boyList = new ArrayList<LuckBoy>(); 

   ---

4. LuckBoy boy1 = new LuckBoy("张三",13,"上海"); 

   ---

5. LuckBoy boy2 = new LuckBoy("李四",12,"北京"); 

   ---

6. LuckBoy boy3 = new LuckBoy("王五",18,"深圳"); 

   ---

7. LuckBoy boy4 = new LuckBoy("马六",17,"南京"); 

   ---

8.  

   ---

9. boyList.add(boy1); 

   ---

10. boyList.add(boy2); 

    ---

11. boyList.add(boy3); 

    ---

12. boyList.add(boy4); 

    ---

13.  

    ---

14. System.out.println("排序前:"); 

    ---

15. for (LuckBoy luckBoy : boyList) { 

    ---

16. System.out.println(luckBoy); 

    ---

17. } 

    ---

18.  

    ---

19. System.out.println("排序后:"); 

    ---

20. Collections.sort(boyList, new LuckBoyCompare()); 

    ---

21. for (LuckBoy luckBoy : boyList) { 

    ---

22. System.out.println(luckBoy); 

    ---

23. } 

    ---

24. } 

    ---

LuckBoy.java

1. package sort; 

   ---

2.  

   ---

3. public class LuckBoy{ 

   ---

4. private String name; 

   ---

5. private Integer age; 

   ---

6. private String city; 

   ---

7.  

   ---

8. public LuckBoy() { 

   ---

9. super(); 

   ---

10. } 

    ---

11.  

    ---

12. public LuckBoy(String name, Integer age, String city) { 

    ---

13. super(); 

    ---

14. this.name = name; 

    ---

15. this.age = age; 

    ---

16. this.city = city; 

    ---

17. } 

    ---

18.  

    ---

19. public String getName() { 

    ---

20. return name; 

    ---

21. } 

    ---

22. public void setName(String name) { 

    ---

23. this.name = name; 

    ---

24. } 

    ---

25. public Integer getAge() { 

    ---

26. return age; 

    ---

27. } 

    ---

28. public void setAge(Integer age) { 

    ---

29. this.age = age; 

    ---

30. } 

    ---

31. public String getCity() { 

    ---

32. return city; 

    ---

33. } 

    ---

34. public void setCity(String city) { 

    ---

35. this.city = city; 

    ---

36. } 

    ---

37.  

    ---

38. @Override 

    ---

39. public String toString() { 

    ---

40. return "LuckBoy [name=" + name + ", age=" + age + ", city=" + city + "]"; 

    ---

41. } 

    ---

42. } 

    ---

打印结果:

排序前:
LuckBoy [name=张三, age=13, city=上海]
LuckBoy [name=李四, age=12, city=北京]
LuckBoy [name=王五, age=18, city=深圳]
LuckBoy [name=马六, age=17, city=南京]
排序后:
LuckBoy [name=李四, age=12, city=北京]
LuckBoy [name=张三, age=13, city=上海]
LuckBoy [name=马六, age=17, city=南京]
LuckBoy [name=王五, age=18, city=深圳]

Comparable接口

使用步骤:

• 数据模型实现Comparable接口,
• 重写compareTo方法,

1. package sort; 

   ---

2.  

   ---

3. public class LuckBoy implements Comparable<LuckBoy>{ 

   ---

4. //TODO 中间代码省略 

   ---

5. @Override 

   ---

6. public int compareTo(LuckBoy o) { 

   ---

7. return this.age-o.age; 

   ---

8. } 

   ---

9. } 

   ---

10.  

    ---

• 调用Collections.sort()方法进行排序,
• 形式:Collections.sort(集合)

1. @Test 

   ---

2. public void test2() { 

   ---

3. List<LuckBoy> boyList = new ArrayList<LuckBoy>(); 

   ---

4. LuckBoy boy1 = new LuckBoy("张三",13,"上海"); 

   ---

5. LuckBoy boy2 = new LuckBoy("李四",12,"北京"); 

   ---

6. LuckBoy boy3 = new LuckBoy("王五",18,"深圳"); 

   ---

7. LuckBoy boy4 = new LuckBoy("马六",17,"南京"); 

   ---

8.  

   ---

9. boyList.add(boy1); 

   ---

10. boyList.add(boy2); 

    ---

11. boyList.add(boy3); 

    ---

12.  

    ---

13. boyList.add(boy4); 

    ---

14.  

    ---

15. System.out.println("============================"); 

    ---

16. System.out.println("排序前:"); 

    ---

17. for (LuckBoy luckBoy : boyList) { 

    ---

18. System.out.println(luckBoy); 

    ---

19. } 

    ---

20.  

    ---

21. System.out.println("排序后:"); 

    ---

22. Collections.sort(boyList); 

    ---

23. for (LuckBoy luckBoy : boyList) { 

    ---

24. System.out.println(luckBoy); 

    ---

25. } 

    ---

26. } 

    ---

打印结果:

排序前:
LuckBoy [name=张三, age=13, city=上海]
LuckBoy [name=李四, age=12, city=北京]
LuckBoy [name=王五, age=18, city=深圳]
LuckBoy [name=马六, age=17, city=南京]
排序后:
LuckBoy [name=李四, age=12, city=北京]
LuckBoy [name=张三, age=13, city=上海]
LuckBoy [name=马六, age=17, city=南京]
LuckBoy [name=王五, age=18, city=深圳]

区别

Comparator 使用灵活,不需要修改源码.但是,使用时需要传入比较器对象;
Comparable 使用简单,但是需要修改源码.