枚举类

1.枚举类入门

Java枚举类是从Java5开始支持的。

枚举类的构造方法是用private修饰的。枚举类的所有实例必须在类的第一行列出，否则这个枚举类不会产生对象。

而且这些实例都是public static void.

每个枚举类都有一个values方法，该方法可以遍历枚举类的所有实例

[java] view plaincopyprint?

1. public class Test {

2.  

3.  

4. public static void tell(Season s)

5. {

6. switch(s)

7. {

8. case Spring:

9. System.out.println(s+"春天");

10. break;

11. case Summer:System.out.println(s+"夏天");

12. break;

13. case Fall:System.out.println(s+"秋天");

14. break;

15. case Winter:System.out.println(s+"冬天");

16. break;

17. }

18.  

19. }

20.  

21. public static void main(String[] args) {

22.  

23. for(Season s:Season.values())

24. {

25. System.out.println(s);

26. }

27. tell(Season.Fall);

28.  

29. }

30.  

31. }

32.  

33. enum Season

34. {

35. Spring,Summer,Fall,Winter;

36. }

public class Test {
	
	
	public static void tell(Season s)
	{
		switch(s)
		{
		case Spring:
			System.out.println(s+"春天");
			break;
		case Summer:System.out.println(s+"夏天");
			break;
		case Fall:System.out.println(s+"秋天");
			break;
		case Winter:System.out.println(s+"冬天");
			break;
		}
		
	}
	
	public static void main(String[] args) {
		
		for(Season s:Season.values())
		{
			System.out.println(s);
		}
		tell(Season.Fall);

	}

}

enum Season
{
	Spring,Summer,Fall,Winter;
}

2.枚举类的构造方法和对象

枚举类的构造方法是private，所以不能使用new创建对象

可以使用Enum.valueOf(Class c,String s);创建对象

[java] view plaincopyprint?

1. public class Test {

2.  

3.  

4.  

5.  

6.  

7. public static void main(String[] args) {

8.  

9.  

10. Season s=Enum.valueOf(Season.class, "Summer");

11. System.out.println(s);

12.  

13. }

14.  

15. }

16.  

17. enum Season

18. {

19. Spring,Summer,Fall,Winter;

20. }

public class Test {
	
	
	
		
	
	public static void main(String[] args) {

		
		Season s=Enum.valueOf(Season.class, "Summer");
		System.out.println(s);

	}

}

enum Season
{
	Spring,Summer,Fall,Winter;
}

一旦为枚举类定义了带参数的构造方法后，列举枚举类就必须对应的传入参数

[java] view plaincopyprint?

1. public class Test {

2.  

3.  

4.  

5.  

6.  

7. public static void main(String[] args) {

8.  

9. Season s=Enum.valueOf(Season.class, "Summer");

10. System.out.println(s.name);

11.  

12. }

13.  

14. }

15.  

16. enum Season

17. {

18. Spring("春天"),Summer("夏天"),Fall("秋天"),Winter("冬天");

19. public String name;

20. private Season(String name)

21. {

22. this.name=name;

23. }

24. }

public class Test {
	
	
	
		
	
	public static void main(String[] args) {
		
		Season s=Enum.valueOf(Season.class, "Summer");
		System.out.println(s.name);

	}

}

enum Season
{
	Spring("春天"),Summer("夏天"),Fall("秋天"),Winter("冬天");
	public String name;
	private Season(String name)
	{
		this.name=name;
	}
}

3.枚举类实现接口

与普通类一样，枚举类实现接口，则必须实现接口中所有的方法

[java] view plaincopyprint?

1. public class Test {

2.  

3.  

4.  

5.  

6.  

7. public static void main(String[] args) {

8.  

9. Season s=Enum.valueOf(Season.class, "Summer");

10. System.out.println(s.name);

11. s.printInfo();

12.  

13. }

14.  

15. }

16.  

17. enum Season implements Infomation

18. {

19. Spring("春天"),Summer("夏天"),Fall("秋天"),Winter("冬天");

20. public String name;

21. private Season(String name)

22. {

23. this.name=name;

24. }

25. @Override

26. public void printInfo() {

27. System.out.println(name);

28.  

29. }

30. }

31. interface Infomation

32. {

33. void printInfo();

34. }

public class Test {
	
	
	
		
	
	public static void main(String[] args) {
		
		Season s=Enum.valueOf(Season.class, "Summer");
		System.out.println(s.name);
		s.printInfo();

	}

}

enum Season implements Infomation
{
	Spring("春天"),Summer("夏天"),Fall("秋天"),Winter("冬天");
	public String name;
	private Season(String name)
	{
		this.name=name;
	}
	@Override
	public void printInfo() {
		System.out.println(name);
		
	}
}
interface Infomation
{
	void printInfo();
}

也可以使用匿名内部类的方法为每一个枚举类对象实现接口

[java] view plaincopyprint?

1. public class Test {

2.  

3.  

4.  

5.  

6.  

7. public static void main(String[] args) {

8.  

9. Season s=Enum.valueOf(Season.class, "Summer");

10. System.out.println(s.name);

11. s.printInfo();

12.  

13. }

14.  

15. }

16.  

17. enum Season implements Infomation

18. {

19. Spring("春天"){

20.  

21. @Override

22. public void printInfo() {

23. // TODO Auto-generated method stub

24. System.out.println("春天温暖");

25.  

26. }

27.  

28. },Summer("夏天")

29. {

30.  

31. @Override

32. public void printInfo() {

33. // TODO Auto-generated method stub

34. System.out.println("夏天炎热");

35. }

36.  

37. },Fall("秋天")

38. {

39.  

40. @Override

41. public void printInfo() {

42. // TODO Auto-generated method stub

43. System.out.println("秋天凉爽");

44. }

45.  

46. },Winter("冬天"){

47.  

48. @Override

49. public void printInfo() {

50. // TODO Auto-generated method stub

51. System.out.println("冬天寒冷");

52. }

53.  

54. };

55. public String name;

56. private Season(String name)

57. {

58. this.name=name;

59. }

60.  

61. }

62. interface Infomation

63. {

64. void printInfo();

65. }

public class Test {
	
	
	
		
	
	public static void main(String[] args) {
		
		Season s=Enum.valueOf(Season.class, "Summer");
		System.out.println(s.name);
		s.printInfo();

	}

}

enum Season implements Infomation
{
	Spring("春天"){

		@Override
		public void printInfo() {
			// TODO Auto-generated method stub
			System.out.println("春天温暖");
			
		}
		
	},Summer("夏天")
	{

		@Override
		public void printInfo() {
			// TODO Auto-generated method stub
			System.out.println("夏天炎热");
		}
		
	},Fall("秋天")
	{

		@Override
		public void printInfo() {
			// TODO Auto-generated method stub
			System.out.println("秋天凉爽");
		}
		
	},Winter("冬天"){

		@Override
		public void printInfo() {
			// TODO Auto-generated method stub
			System.out.println("冬天寒冷");
		}
		
	};
	public String name;
	private Season(String name)
	{
		this.name=name;
	}
	
}
interface Infomation
{
	void printInfo();
}

4.包含抽象方法的枚举类

包含抽象方法枚举类，要实例化对象的话，就得让每个对象实现抽象方法

[java] view plaincopyprint?

1. public class Test {

2.  

3.  

4.  

5.  

6.  

7. public static void main(String[] args) {

8.  

9. Season s=Enum.valueOf(Season.class, "Summer");

10. System.out.println(s.name);

11. s.printInfo();

12. s.whatToDo();

13.  

14. }

15.  

16. }

17.  

18. enum Season implements Infomation

19. {

20. Spring("春天"){

21.  

22. @Override

23. public void printInfo() {

24. // TODO Auto-generated method stub

25. System.out.println("春天温暖");

26.  

27. }

28.  

29. @Override

30. public void whatToDo() {

31. // TODO Auto-generated method stub

32. System.out.println("我去春游");

33.  

34. }

35.  

36. },Summer("夏天")

37. {

38.  

39. @Override

40. public void printInfo() {

41. // TODO Auto-generated method stub

42. System.out.println("夏天炎热");

43. }

44.  

45. @Override

46. public void whatToDo() {

47. // TODO Auto-generated method stub

48. System.out.println("我去游泳");

49. }

50.  

51. },Fall("秋天")

52. {

53.  

54. @Override

55. public void printInfo() {

56. // TODO Auto-generated method stub

57. System.out.println("秋天凉爽");

58. }

59.  

60. @Override

61. public void whatToDo() {

62. // TODO Auto-generated method stub

63. System.out.println("我去玩乒乓球");

64. }

65.  

66. },Winter("冬天"){

67.  

68. @Override

69. public void printInfo() {

70. // TODO Auto-generated method stub

71. System.out.println("冬天寒冷");

72. }

73.  

74. @Override

75. public void whatToDo() {

76. // TODO Auto-generated method stub

77. System.out.println("我去赏雪观梅");

78. }

79.  

80. };

81. public String name;

82. private Season(String name)

83. {

84. this.name=name;

85. }

86. public abstract void whatToDo();

87.  

88. }

89. interface Infomation

90. {

91. void printInfo();

92. }