Readable接口的使用

Thinking in Java(6)

1.1 Readable接口简单应用

如果一个类继承了readable接口并实现了read方法，我们就可以使用scanner类来进行操作。read方法返回小于0的数表示没有可以读取的，s.hasNext就会退出，简单示例如下。

import java.io.*;
import java.util.*;
import java.nio.CharBuffer;

public class RandomString implements Readable{
	private static char[] str = "ABC".toCharArray();
	private Random rand = new Random(47);
	private int count = 0;                           //产生随机字符串的个数
	
	public RandomString(int count) {
		this.count = count;
	}
	
	//Readable需要实现read方法
	@Override
	public int read(CharBuffer arg0) {
		// TODO Auto-generated method stub
		count--;
		if(count < 0) return -1;     //返回-1  结束
		for(int i=0; i<5; i++) {
			arg0.append(str[rand.nextInt(str.length)]);
		}
		arg0.append(' ');
		return 1;
	}
	
	public static void main(String[] args) {
		Scanner s = new Scanner(new RandomString(4));
		while(s.hasNext()) {
			System.out.println(s.next());
		}
	}
}

1.2 使用适配器使用Readable接口

假设我们现在有一个random double的类如下
RandomDoubles.java

import java.io.*;
import java.util.*;


//可以产生随机double数据的类
public class RandomDoubles {
	private static Random rand = new Random(47);
	public double next() {
		return rand.nextDouble();
	}
	public static void main(String[] args) {
		RandomDoubles rd = new RandomDoubles();
		for(int i=0; i<7; i++) {
			System.out.println(rd.next());
		}
	}
}

适配器类

import java.io.IOException;
import java.nio.CharBuffer;
import java.util.Scanner;

//适配器模式 使用Readable接口

public class AdaptedRandomDoubles extends RandomDoubles implements Readable {
	private int count;
	public AdaptedRandomDoubles(int count) {
		this.count = count;
	}
	@Override
	public int read(CharBuffer cb) {
		// TODO Auto-generated method stub
		count--;
		if(count < 0) return -1;
		String result = Double.toString(next()) + " ";
		cb.append(result);
		return result.length();
	}
	public static void main(String[] args) {
		Scanner s = new Scanner(new AdaptedRandomDoubles(10));
		while(s.hasNext()) {
			System.out.println(s.next());
		}
	}
}