Java枚举

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枚举比较简单用一个Demo来学习：

枚举类型定义：

package com.google.www.javacore.enumtest;/** * Created by dell on 2016/12/10. */public enum Size{    /**     * 小号     */    SMALL("S"),    /**     *中号     */    MEDIUM("M"),    /**     * 大号     */    LARGE("L"),    /**     * 超大号     */    EXTRA_LARGE("EL");    Size(String name)    {        this.name = name;    }    String name;    public String getName()    {        return name;    }}

枚举类型的使用举例：

package com.google.www.javacore.enumtest;import java.util.Scanner;/** * Created by dell on 2016/12/10. */public class EnumDemo{    public static void main(String[] args)    {        Scanner in = new Scanner(System.in);        System.out.println("Enter a SIZE: ");        String input = in.next().toUpperCase();        //valueof方法返回该枚举类型的对应常量值，若input非法直接抛出异常        Size s = (Size) Enum.valueOf(Size.class, input);        //toString方法直接返回该常量的字符串        System.out.println("Size = " + s);        System.out.println("The name of " + s +" is " + s.getName());        //比较两个枚举值常量时直接用==来比较，不用equals方法来比较。        if (Size.LARGE == s)        {            System.out.println("The size is Large.");        }    }}

附Enum的valueof方法：

    /**     * Returns the enum constant of the specified enum type with the     * specified name.  The name must match exactly an identifier used     * to declare an enum constant in this type.  (Extraneous whitespace     * characters are not permitted.)     *     * <p>Note that for a particular enum type {@code T}, the     * implicitly declared {@code public static T valueOf(String)}     * method on that enum may be used instead of this method to map     * from a name to the corresponding enum constant.  All the     * constants of an enum type can be obtained by calling the     * implicit {@code public static T[] values()} method of that     * type.     *     * @param <T> The enum type whose constant is to be returned     * @param enumType the {@code Class} object of the enum type from which     *      to return a constant     * @param name the name of the constant to return     * @return the enum constant of the specified enum type with the     *      specified name     * @throws IllegalArgumentException if the specified enum type has     *         no constant with the specified name, or the specified     *         class object does not represent an enum type     * @throws NullPointerException if {@code enumType} or {@code name}     *         is null     * @since 1.5     */    public static <T extends Enum<T>> T valueOf(Class<T> enumType,                                                String name) {        T result = enumType.enumConstantDirectory().get(name);        if (result != null)            return result;        if (name == null)            throw new NullPointerException("Name is null");        throw new IllegalArgumentException(            "No enum constant " + enumType.getCanonicalName() + "." + name);    }

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