fibonacci7.java

来自「JAVA编程思想第四版英文原版习题答案. pdf原版的」· Java 代码 · 共 41 行

// generics/Fibonacci7.java
// TIJ4 Chapter Generics, Exercise 7, page 631
// Use composition instead of inheritance to adapt Fibonacci
// to make it interable.
import net.mindview.util.*;
import java.util.*;

public class Fibonacci7 implements Generator<Integer>, Iterable<Integer> {
	private int count = 0;
	private int m;
	public Integer next() { return fib(count++); }
	private int fib(int n) {
		if(n < 2) return 1;
		return fib(n - 2) + fib(n - 1);
	}
	public Fibonacci7() {}
	public Fibonacci7(int m) { this.m = m; }
	public Iterator<Integer> iterator() {
		return new Iterator<Integer>() {
			public boolean hasNext() { return m > 0; }
			public Integer next() {
				m--;
				return Fibonacci7.this.next();
			}
			public void remove() { // Not implemented
				throw new UnsupportedOperationException();
			}
		};
	}

	public static void main(String[] args) {
		Fibonacci7 gen = new Fibonacci7();
		for(int i = 0; i < 18; i++)
			System.out.print(gen.next() + " ");
		System.out.println();
		Iterator it = new Fibonacci7(20).iterator();
		while(it.hasNext())
			System.out.print(it.next() + " ");
	}
	
}