Java實例講解枚舉enum的實現(xiàn)
一.枚舉介紹
1.枚舉是一組常量的集合
2.理解:美劇屬于一種特殊的類,里面只包含一組有限的特定的對象
1.自定義枚舉實現(xiàn)
1.不需要提供Set方法,枚舉對象值通常為只讀。
2.對枚舉對象/屬性使用final和static關(guān)鍵字修飾,實現(xiàn)底層優(yōu)化
3.枚舉對象名通常使用全部大寫,常量的命名規(guī)范
4.枚舉·對象根據(jù)需要,可以有一到多個屬性
(1)示例
package com.demo; import javax.sound.midi.Soundbank; /** * @version 1.0 * @auther Demo龍 */ public class Enum01 { public static void main(String[] args) { System.out.println(Season.SPRING); System.out.println(Season.SUMMER); System.out.println(Season.AUTUMN); System.out.println(Season.WINTER); } } //演示自定義枚舉實現(xiàn) class Season{ private String name; private String desc;//描述特性 //1.將構(gòu)造器私有化,目的防止直接new出來 private Season(String name, String desc) { this.name = name; this.desc = desc; } //2.去掉set方法,只能讀取,不能修改屬性 public String getName() { return name; } public String getDesc() { return desc; } //3.在season內(nèi)部創(chuàng)建固定的對象 //定義了四個對象 // public static Season SPRING=new Season("春天","溫暖"); // public static Season SUMMER=new Season("夏天","炎熱"); // public static Season AUTUMN=new Season("秋天","涼爽"); // public static Season WINTER=new Season("冬天","寒冷"); //最終優(yōu)化,加入final public static final Season SPRING=new Season("春天","溫暖"); public static final Season SUMMER=new Season("夏天","炎熱"); public static final Season AUTUMN=new Season("秋天","涼爽"); public static final Season WINTER=new Season("冬天","寒冷"); //重寫toString方法 @Override public String toString() { return "Season{" + "name='" + name + '\'' + ", desc='" + desc + '\'' + '}'; } }
(2)測試結(jié)果
2.enum關(guān)鍵字實現(xiàn)枚舉
如果使用enum關(guān)鍵字來實現(xiàn)枚舉類
1.使用關(guān)鍵字enum替換class
2.public static final Season02 SPRING=new Season02(“春天”,“溫暖”);可替換為 SPRING(“春天”,“溫暖”),//解讀:常量名(實參列表)
3.如果有多個常量使用逗號間隔即可
4.如果使用enum關(guān)鍵字實現(xiàn)枚舉,要求將定義的常量對象寫下前面
(1)示例
package com.demo; /** * @version 1.0 * @auther Demo龍 */ public class Enum02 { public static void main(String[] args) { System.out.println(Season.SPRING); System.out.println(Season.SUMMER); System.out.println(Season.AUTUMN); System.out.println(Season.WINTER); } } //演示使用enum關(guān)鍵字來實現(xiàn)枚舉類 enum Season02{ //如果使用enum關(guān)鍵字來實現(xiàn)枚舉類 //1.使用關(guān)鍵字enum替換class //2.public static final Season02 SPRING=new Season02("春天","溫暖");可替換為 SPRING("春天","溫暖"),//解讀:常量名(實參列表) //3.如果有多個常量使用逗號間隔即可 SUMMER("夏天","炎熱"), AUTUMN("秋天","涼爽"), WINTER("冬天","寒冷"); //4.如果使用enum關(guān)鍵字實現(xiàn)枚舉,要求將定義的常量對象寫下前面 private String name; private String desc;//描述特性 //1.將構(gòu)造器私有化,目的防止直接new出來 private Season02(String name, String desc) { this.name = name; this.desc = desc; } //2.去掉set方法,只能讀取,不能修改屬性 public String getName() { return name; } public String getDesc() { return desc; } //3.在season內(nèi)部創(chuàng)建固定的對象 //定義了四個對象 // public static Season SPRING=new Season("春天","溫暖"); // public static Season SUMMER=new Season("夏天","炎熱"); // public static Season AUTUMN=new Season("秋天","涼爽"); // public static Season WINTER=new Season("冬天","寒冷"); //最終優(yōu)化,加入final // public static final Season02 SPRING=new Season02("春天","溫暖"); // public static final Season02 SUMMER=new Season02("夏天","炎熱"); // public static final Season02 AUTUMN=new Season02("秋天","涼爽"); // public static final Season02 WINTER=new Season02("冬天","寒冷"); //重寫toString方法 @Override public String toString() { return "Season{" + "name='" + name + '\'' + ", desc='" + desc + '\'' + '}'; } }
(2)測試結(jié)果
3.enum關(guān)鍵字注意事項
1.當(dāng)我i們使用enum關(guān)鍵字開發(fā)一個枚舉類時,默認(rèn)會繼承Enum類
2.傳統(tǒng)的public static final Season02 SPRING=new Season02("春天","溫暖");
,這里要知道他調(diào)用的是哪個構(gòu)造器
3.如果使用無參構(gòu)造器創(chuàng)建枚舉對象,則實參列表和小括號都可以省略.
4.當(dāng)有多個枚舉對象時,使用逗號間隔,最后有一個分號結(jié)尾
5.枚舉對象必須放在枚舉類的行首
(1)示例
package com.demo; /** * @version 1.0 * @auther Demo龍 */ public class Enum02 { public static void main(String[] args) { System.out.println(Season.SPRING); System.out.println(Season.SUMMER); System.out.println(Season.AUTUMN); System.out.println(Season.WINTER); } } //演示使用enum關(guān)鍵字來實現(xiàn)枚舉類 enum Season02{ //如果使用enum關(guān)鍵字來實現(xiàn)枚舉類 //1.使用關(guān)鍵字enum替換class //2.public static final Season02 SPRING=new Season02("春天","溫暖");可替換為 SPRING("春天","溫暖"),//解讀:常量名(實參列表) //3.如果有多個常量使用逗號間隔即可 SUMMER("夏天","炎熱"), AUTUMN("秋天","涼爽"), WINTER("冬天","寒冷"), //3.如果使用無參構(gòu)造器創(chuàng)建枚舉對象,則實參列表和小括號都可以省略.兩種寫法 HAHA,//調(diào)用無參構(gòu)造器 HAHAHA();//調(diào)用無參構(gòu)造器 //4.如果使用enum關(guān)鍵字實現(xiàn)枚舉,要求將定義的常量對象寫下前面 private String name; private String desc;//描述特性 //1.將構(gòu)造器私有化,目的防止直接new出來 private Season02(String name, String desc) { this.name = name; this.desc = desc; } private Season02() { //無參構(gòu)造器 } //2.去掉set方法,只能讀取,不能修改屬性 public String getName() { return name; } public String getDesc() { return desc; } //3.在season內(nèi)部創(chuàng)建固定的對象 //定義了四個對象 // public static Season SPRING=new Season("春天","溫暖"); // public static Season SUMMER=new Season("夏天","炎熱"); // public static Season AUTUMN=new Season("秋天","涼爽"); // public static Season WINTER=new Season("冬天","寒冷"); //最終優(yōu)化,加入final // public static final Season02 SPRING=new Season02("春天","溫暖"); // public static final Season02 SUMMER=new Season02("夏天","炎熱"); // public static final Season02 AUTUMN=new Season02("秋天","涼爽"); // public static final Season02 WINTER=new Season02("冬天","寒冷"); //重寫toString方法 @Override public String toString() { return "Season{" + "name='" + name + '\'' + ", desc='" + desc + '\'' + '}'; } }
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