枚举的一些用法

小鱼儿 2022-08-06 07:23 299阅读 0赞

枚举策略模式：

package com.price.effective.enum1;
    
    public enum Pay {
    	MONDAY(PayType.WEEKDAY),
    	SUNDAY(PayType.WEEKEND);
    	
    	private PayType payType;
    	
    	Pay(PayType payType){
    		this.payType = payType;
    	}
    	
    	double pay(double hoursworked, double payRate){
    		return payType.overPay(hoursworked - 8, payRate) + payRate*8;
    	}
    	
    	private enum PayType{
    		WEEKEND{
    			@Override
    			double overPay(double hours, double payRate) {
    				return hours * payRate * 3;
    			}
    		},
    		
    		WEEKDAY{
    
    			@Override
    			double overPay(double hours, double payRate) {
    				return hours * payRate;
    			}
    			
    		};
    		
    		abstract double overPay(double hours, double payRate);
    	}
    }

枚举值域

package com.price.effective.enum1;
    
    import java.util.EnumSet;
    import java.util.Set;
    
    public class TestEnumSet {
    	// 一般的结合是List或者Set, 还有种跟好的办法如下：
    	public static final int STYLE_BOLD = 1 << 0;
    	public static final int STYLE_ITALIC = 1 << 1;
    	// 这样就能够使用位运算来得到一个int型表示的集合，效率较高
    	public void applyStyles(int styles){
    		if((styles & STYLE_BOLD) != 0){
    			System.out.println("BOLD");
    		}
    		if((styles & STYLE_ITALIC) != 0){
    			System.out.println("ITALIC");
    		}
    	}
    	
    	
    	// 下面用EnumSet来实现以下
    	public enum Style{BOLD, ITALIC};
    	
    	public void applyStyles(Set<Style> styles){
    		if(styles.contains(Style.BOLD)){
    			System.out.println("BOLD");
    		}
    		if(styles.contains(Style.ITALIC)){
    			System.out.println("ITALIC");
    		}
    	}
    	
    	public static void main(String[] args) {
    		TestEnumSet tes = new TestEnumSet();
    		tes.applyStyles(TestEnumSet.STYLE_BOLD | TestEnumSet.STYLE_ITALIC);
    		tes.applyStyles(EnumSet.of(Style.BOLD, Style.ITALIC));
    	}
    }

枚举作为Map的key:

package com.price.effective.enum1;
    
    import java.util.ArrayList;
    import java.util.Collection;
    import java.util.EnumMap;
    import java.util.List;
    import java.util.Map;
    
    /**
     * 给动物分类
     *
     * @author cdwangzijian
     *
     */
    public class TestEnumMap {
    	public static void main(String[] args) {
    		// 一种方式是便利所有的动物，根据类型加入到对应的集合中
    		// 稍微好一点的可能可以利用类型名称数组来分类，如下：
    		List<Animal>[] animalByType = new List[Animal.Type.values().length];
    		for (int i = 0 ; i < animalByType.length; i++) {
    			animalByType[i] = new ArrayList<Animal>();
    		}
    		for (Animal a : Animal.getAnimals()) {
    			animalByType[a.getType().ordinal()].add(a);
    		}
    		
    		printResult(animalByType);
    		
    		
    		Map<Animal.Type, Animal> animalTypeMap = new EnumMap<Animal.Type, Animal>(Animal.Type.class);
    		for (Animal a : Animal.getAnimals()) {
    			animalTypeMap.put(a.getType(), a);
    		}
    		
    		printResult(animalTypeMap.values());
    	}
    
    	private static void printResult(Collection<Animal> values) {
    		System.out.println(values);
    	}
    
    	private static void printResult(List<Animal>[] animalByType) {
    		for (List<Animal> as : animalByType) {
    			System.out.println(as);
    		}
    	}
    }
    
    class Animal{
    	public static enum Type{LINGZHANG, CAT, FLY};
    	private String name;
    	private Type type;
    	
    	public Animal(String name, Type type) {
    		this.name = name;
    		this.type = type;
    	}
    
    	public String getName() {
    		return name;
    	}
    
    	public void setName(String name) {
    		this.name = name;
    	}
    
    	public Type getType() {
    		return type;
    	}
    
    	public void setType(Type type) {
    		this.type = type;
    	}
    	
    	@Override
    	public String toString() {
    		return "name:" + name;
    	}
    	public static List<Animal> getAnimals(){
    		Animal tiger = new Animal("tiger", Animal.Type.CAT);
    		Animal chiken = new Animal("chiken", Animal.Type.LINGZHANG);
    		Animal monkey = new Animal("monkey", Animal.Type.FLY);
    		List<Animal> animals = new ArrayList<Animal>();
    		animals.add(tiger);
    		animals.add(chiken);
    		animals.add(monkey);
    		return animals;
    	}
    }