枚举

1.枚举简介

枚举由一组固定的常量组成的类型,自定义数据类型,

枚举的常量值一定是可列举的有限值。常量值的类型都是public static final

 

[修饰符] enum enumName{
  常量值1,
  常量值2,
  常量值3…
  
  常量值n[;]
}

  

Gender 是一种自定义的数据类型,可以用于声明变量,且变量的取值必须是枚举值的其中一个。gender的值必须是男或者女或者保密。

public static void main(String[] args) {
		
		// 声明一个Gender枚举类型的变量gender,并取值为男
		Gender gender = Gender.男;
	}

 

  

java中所有的枚举类型都继承于Enum类。可以把枚举类型看出一个类。

public class Student {

	private String name;
	private int age;
	private Gender gender;

	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 Gender getGender() {
		return gender;
	}

	public void setGender(Gender gender) {
		this.gender = gender;
	}

	public Student(String name, int age, Gender gender) {
		super();
		this.name = name;
		this.age = age;
		this.gender = gender;
	}

	public Student() {
		super();
	}

	@Override
	public String toString() {
		return "Student [name=" + name + ", age=" + age + ", gender=" + gender + "]";
	}

}

// class Gender extends Enum{}
enum Gender {
	男, 女, 保密;
}

  

1.2 枚举和字符串转化

public static void main(String[] args) {
		
		// 声明一个Gender枚举类型的变量gender,并取值为男
		Gender gender = Gender.男;
		
		
		// 枚举值->字符串
		System.out.println(gender.toString());
		
		// 字符串串-> 枚举值
		String str = "保密";
		// 可能产生IllegalArgumentException 非法参数异常
		Gender gender2 = Enum.valueOf(Gender.class, str);
		System.out.println(gender2);
		
	}

 

  

1.3 枚举switch

public enum Week {
	MONDAY,
	TUESDAY,
	WEDNESDAY,
	THURSDAY,
	FRIDAY,
	SATURDAY,
	SUNDAY;
}
public static void main(String[] args) {
		
		
		// 需求:有一个变量表示星期几,输出对于的教学安排
		Week week = Week.TUESDAY;
		switch (week) {
			case MONDAY:
			case TUESDAY:
			case THURSDAY:
			case FRIDAY:
			case SATURDAY:{
				System.out.println("上课");
				break;
			}
			case WEDNESDAY:
			case SUNDAY:{
				System.out.println("练习");
				break;
			}
		}
	}

  

枚举的其他方法

public static void main(String[] args) {
				
		// 枚举变量的其他方法
		Week week = Week.SUNDAY;
		System.out.println(week.name());
		System.out.println(week.ordinal());
	}

  

 

 

posted @ 2019-04-29 22:14  麻烦关下灯  阅读(134)  评论(0编辑  收藏  举报