查询最长单词链

package wordslian;


import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

public class lian {

	public static void main(String[] args) throws IOException {
		// TODO 自动生成的方法存根

		String filename ="D:\input.txt";
		File  a=new  File(filename);
	 //judeFileExists(a);
	 if(judeFileExists(a))
		 
		{
			danci(filename);
		}
	 else
	    {}
	 	
		
	}

	public static void danci(String s) throws IOException {
		   int num=0;
			BufferedReader br = new BufferedReader(new FileReader(s));
			StringBuffer sb = new StringBuffer();
			String text = null;
			while ((text = br.readLine()) != null) {
				num++;
				sb.append(text);// 将读取出的字符追加到stringbuffer中
			}
			br.close(); // 关闭读入流
			String str = sb.toString().toLowerCase(); // 将stringBuffer转为字符并转换为小写
			String[] words = str.split("[^(a-zA-Z)]+"); // 非单词的字符来分割，得到所有单词
			StringBuffer yao = new StringBuffer();
			String b1=words[0];
			yao.append(b1);
			yao.append(" ");
			//System.out.println(b1);
			String end=b1.substring(b1.length()-1,b1.length());
		    //System.out.println(end);
		   for(int i=1;i<words.length;i++)
		   {  
		    String start=words[i].substring(0,1);
		    if(end.equals(start))
		    {
		    	end=words[i].substring(words[i].length()-1,words[i].length());
		    	yao.append(words[i]);
		    	yao.append(" ");
		    	
		    }
		   }
		   
		  // for( String a:words)
		  // {
			 //  System.out.println(a);
		//   }
		 //  System.out.println(yao.toString()); 
		   File file =new File("D:\output.txt");
	        try {
	             file.createNewFile();
	        } catch (IOException e) {
	           e.printStackTrace();      
	       }
	      
	        try {
	        	
	        	  FileWriter fw =new FileWriter(file);
	        	  fw.write(yao.toString());
	        	  fw.flush();
	        	  fw.close();
	        }
	        catch (IOException e) {
		           e.printStackTrace();      
		       }
	        System.out.println(num);
	     
	}


// 判断文件是否存在
public static boolean judeFileExists(File file) {

    if (file.exists()) {
        System.out.println("请查看输出文件");
        return true;
    } else {
        System.out.println("文件不存在");
        // try {
        //     file.createNewFile();
       //  } catch (IOException e) {
       // TODO Auto-generated catch block
      //      e.printStackTrace();      
     //   }
        return false;
    }
}
// 判断文件夹是否存在(未修改)
public static void judeDirExists(File file) {

    if (file.exists()) {
        if (file.isDirectory()) {
            System.out.println("dir exists");
        } else {
            System.out.println("the same name file exists, can not create dir");
        }
    } else {
        System.out.println("dir not exists, create it ...");
        file.mkdir();
    }

}
}