享元模式

享元模式的目的是为了减少不会要额内存消耗，将多个对同一对象的访问集中起来，不必为每个访问者创建一个单独的对象，以此来降低内存的消耗。分为单纯享元模式和复合享元模式。

单纯享元模式通过一个map来维护对象，获取对象的时候先从map里面找是否有符合的对象，有就直接返回，达到对象的共享，其内蕴状态是不变的，依靠外蕴状态来使共享的对象发生不同的行为。复合享元模式的对象是不能共享的，但是它可以分解成单纯享元对象的组合。常用的String就是享元模式。
示例如下：

public class Flyweight {
    public static void main(String[] args){
        Flyweight flyweight=new Flyweight();
        ComputerComponentsFactory factory = flyweight.new ComputerComponentsFactory();
        ComputerComponents cpu1 = factory.getComponents("CPU");
        ComputerComponents cpu2 = factory.getComponents("CPU");
        ComputerComponents hardDisk1 = factory.getComponents("硬盘");
        ComputerComponents hardDisk2 = factory.getComponents("硬盘");
        System.out.println("cpu1==cpu2 "+(cpu1==cpu2));
        System.out.println("hardDisk1==hardDisk2 "+(hardDisk1==hardDisk2));
        cpu1.getModel("inter");
        cpu2.getModel("AMD");
    }

    abstract class Components{
        private String  part;

        public Components(String  part) {
            this. part =  part;
        }

        public String getPart() {
            return  part;
        }

        public abstract void getModel(String model);
    }

    class ComputerComponents extends Components{
        public ComputerComponents(String part) {
            super(part);
        }

        @Override
        public void getModel(String model) {
            System.out.println("零件"+getPart()+"的型号是"+model);
        }
    }

    class ComputerComponentsFactory{
        private HashMap<String,ComputerComponents> map=new HashMap<>();
        public ComputerComponents getComponents(String key){
            if(map.containsKey(key))
                return map.get(key);
            ComputerComponents computerComponents=new ComputerComponents(key);
            map.put(key,computerComponents);
            return computerComponents;
        }
    }
}