15.4.3 用于Generator的泛型方法

最新推荐文章于 2024-10-30 21:32:52 发布

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最新推荐文章于 2024-10-30 21:32:52 发布

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本文链接：https://blog.youkuaiyun.com/weixin_33669968/article/details/88889942

本文介绍了一个使用Java实现的通用集合填充方法和多种生成器示例，包括咖啡生成器和斐波那契数生成器。通过具体代码演示了如何使用这些生成器填充集合并打印结果。

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package chapter15._4._3;

import chapter15._3.coffee.Coffee;
import chapter15._3.coffee.CoffeeGenerator;
import chapter15._3.coffee.Generator;
import chapter15._3.fibonacci.Fibonacci;

import java.util.ArrayList;
import java.util.Collection;

public class Generators {

    public static <T> Collection<T> fill(Collection<T> coll, Generator<T> gen, int n) {
        for(int i = 0; i < n; i++)
            coll.add(gen.next());
        return coll;
    }

    public static void main(String[] args) {
        Collection<Coffee> coffees = fill(new ArrayList<Coffee>(), new CoffeeGenerator(), 3);
        for (Coffee c : coffees)
            System.out.println(c);

        Collection<Integer> fnumbers = fill(new ArrayList<Integer>(), new Fibonacci(), 5);
        for (Integer f : fnumbers)
            System.out.println(f);
    }

}

Latte 0
Americano 1
Latte 2
1
1
2
3
5

public interface Generator<T> {

    T next();

}

public class Coffee {

    private static long counter = 0;
    private final long id = counter++;

    @Override
    public String toString() {
        return getClass().getSimpleName() + " " + id;
    }
}

public class CoffeeGenerator implements Generator<Coffee>, Iterable<Coffee> {

    private Class[] types = {Americano.class, Breve.class, Cappuccino.class, Latte.class, Mocha.class};

    private int size;

    private static Random random = new Random(47);

    public CoffeeGenerator() {}

    public CoffeeGenerator(int size) {
        this.size = size;
    }

    @Override
    public Coffee next() {
        try {
            return (Coffee) types[random.nextInt(types.length)].newInstance();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    class CoffeeIterator implements Iterator<Coffee> {

        int count = size;

        @Override
        public boolean hasNext() {
            return count > 0;
        }

        @Override
        public Coffee next() {
            count --;
            return CoffeeGenerator.this.next();
        }

    }

    @Override
    public Iterator<Coffee> iterator() {
        return new CoffeeIterator();
    }

}

class CoffeeGeneratorClient {

    public static void main(String[] args) {
        CoffeeGenerator coffeeGenerator = new CoffeeGenerator();
        for(int i = 0; i < 5; i++)
            System.out.println(coffeeGenerator.next());
        for(Coffee c : new CoffeeGenerator(5))
            System.out.println(c);
    }

}

public class Fibonacci implements Generator<Integer> {

    private int count = 0;

    private int fab(int n) {
        if (n < 2)
            return 1;
        return fab(n - 2) + fab(n - 1);
    }

    @Override
    public Integer next() {
        return fab(count++);
    }

    public static void main(String[] args) {
        Fibonacci fibonacci = new Fibonacci();
        for (int i = 0; i < 18; i++)
            System.out.print(fibonacci.next() + " ");
    }

}