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1.枚举类的理解:类的对象只有有限个,确定的。我们称此类为枚举类
2.当需要定义一组常量时,强烈建议使用枚举类
3.如果枚举类中只有一个对象,则可以作为单例模式的实现方式。
方式一:JDK5.0之前,自定义枚举类
public class SeasonTest { public static void main(String[] args) { Season spring = Season.SPRING; System.out.println(spring); } } class Season { //1.声明Season对象的属性:private final修饰 private final String seasonName; private final String seasonDesc; //2.私有化类的构造器,并给对象属性赋值 private Season(String seasonName, String seasonDesc) { this.seasonName = seasonName; this.seasonDesc = seasonDesc; } //3.提供当前枚举类的对各对象:public static final的 public static final Season SPRING = new Season("春天", "春暖花开"); public static final Season SUMMER = new Season("夏天", "夏日炎炎"); public static final Season AUTUMN = new Season("秋天", "秋高气爽"); public static final Season WINTER = new Season("冬天", "冰天雪地"); //4.其他诉求1: 获取枚举类对象的属性 public String getSeasonName() { return seasonName; } public String getSeasonDesc() { return seasonDesc; } //4.其他诉求2:提供toString() @Override public String toString() { return "Season{" + "seasonName='" + seasonName + '\'' + ", seasonDesc='" + seasonDesc + '\'' + '}'; } }
方式二:JDK5.0之后,可以使用enum关键字定义枚举类
public class SeasonTest1 { public static void main(String[] args) { Season1 summer = Season1.SUMMER; System.out.println(summer); System.out.println(Season1.class.getSuperclass());//java.lang.Enum //values(): Season1[] values = Season1.values(); for (int i = 0; i < values.length; i++) { System.out.println(values[i]); } //valueOf(String objName):返回枚举类中对象时objName的对象。 Season1 winter = Season1.valueOf("WINTER"); //如果没有objName的枚举类对象,则抛异常:IllegalArgumentException // Season1 winter = Season1.valueOf("WINTER1"); System.out.println(winter); // winter.show(); } //使用enum关键字定义枚举类 enum Season1 { //1.提供当前枚举类的对象,多个对象之间用","隔开,末尾对象";"结束 SPRING("春天", "春暖花开"), SUMMER("夏天", "夏日炎炎"), AUTUMN("秋天", "秋高气爽"), WINTER("冬天", "冰天雪地"); //1.声明Season对象的属性:private final修饰 private final String seasonName; private final String seasonDesc; //2.私有化类的构造器,并给对象属性赋值 private Season1(String seasonName, String seasonDesc) { this.seasonName = seasonName; this.seasonDesc = seasonDesc; } //4.其他诉求1: 获取枚举类对象的属性 public String getSeasonName() { return seasonName; } public String getSeasonDesc() { return seasonDesc; }
使用enum关键字定义的枚举类实现接口的情况
情况一:实现接口,在enum类中实现抽象方法
情况二:让枚举类的对象分别实现接口中的抽象方法
public class SeasonTest1 { public static void main(String[] args) { //values(): Season1[] values = Season1.values(); for (int i = 0; i < values.length; i++) { System.out.println(values[i]); values[i].show(); } } interface Info { void show(); } enum Season1 implements Info { SPRING("春天", "春暖花开") { @Override public void show() { System.out.println("春天在哪里"); } }, SUMMER("夏天", "夏日炎炎") { @Override public void show() { System.out.println("宁夏"); } }, AUTUMN("秋天", "秋高气爽") { @Override public void show() { System.out.println("秋天不回来"); } }, WINTER("冬天", "冰天雪地") { @Override public void show() { System.out.println("大约在冬季"); } }; private final String seasonName; private final String seasonDesc; private Season1(String seasonName, String seasonDesc) { this.seasonName = seasonName; this.seasonDesc = seasonDesc; } public String getSeasonName() { return seasonName; } public String getSeasonDesc() { return seasonDesc; } }
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