SequenceInputStream 合成器的運用

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

/**
* 自定義的列舉類 支援元素FileInputStream,體現在nextElement()方法上
* 不要暈：類內的私有資料成員支援元素String,我們主要看自定義類上的泛型是FileInputStream,以及體現到方法nextElement()上的返回型別
*/

class MyEnumeration implements Enumeration<FileInputStream>
{
	private Enumeration<String> files;
	public MyEnumeration(Vector<String> files){
		this.files = files.elements();
	}
	public boolean hasMoreElements(){
		return files.hasMoreElements();
	}

	public FileInputStream nextElement(){
		try{
			return new FileInputStream(files.nextElement());
		}catch(Exception e){
			return null;
		}
	}
}

public class SequenceInputStreamDemo 
{
	public static void main(String[] args) 
	{
		int c;
		Vector<String> v = new Vector();
		v.addElement("file1.txt");
		v.addElement("file2.txt");
		v.addElement("file3.txt");

		MyEnumeration en = new MyEnumeration(v);
		
		try(InputStream in = new SequenceInputStream(en)){
			while((c=in.read())!=-1){
				System.out.print((char)c);
			}
		}catch(Exception e){}
	}
}