求最长的单词链

求最长的首尾相接的单词链思路;FileReader fr = new FileReader(f1);

  BufferedReader bReader = new BufferedReader(fr);

while((hasRead=bReader.readLine()) != null){
    sb1.append(hasRead);//将读取的字符串添加换行符后累加p存放在缓存    
    }text.split(" ");根据空格将其分割成一个个单词存放进字符串数组。并用自定义的方法toLowerCase(String str)将每一个单词都转化成小写，并统计每一个单词的首字母和尾字母存进head组数和wei数组。运用双层循环遍历，分别遍历出每个单词作为第一个单词时的最长的单词链，跟根据其中存在的“➕”来判断谁的链组成的单词最多来输出到output.txt文件中。

package 统计英文字母出现频率;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Scanner;



public class Dancilian {
	public static String toLowerCase(String str) {//将字符串统一转化成小写的
		char []StringArr = str.toCharArray();
		for (int i = 0; i < StringArr.length; i++) {
			StringArr[i] = Character.toLowerCase(StringArr[i]);
		}
    	StringBuffer sb = new StringBuffer();
		for(int i = 0;i < StringArr.length;i++) {
			sb.append(StringArr[i]);
		}
		String str1 = sb.toString();
		return str1; 
		
	}
	public static int shuliang(String str) {//统计每个字符串中“➕”的数量，根据“➕”在判断其是由多少个单词相接而成的。
		char []StringArr = str.toCharArray();
		int num = 0;
		for(int i = 0 ;i < StringArr.length;i++) {
			if(StringArr[i] == '+') {
				num++;
			}
		}
		return num;
	}
	public static void FileCaozuo(String infilename,String outfilename) throws IOException {//对文件的操作。
		try { 
			File f1 = new File(infilename);
		if(!f1.exists()) //如果输入文件不存在那么就停止程序的运行
			System.out.println("input.txt文件不存在！");
			System.exit(0);
		}
		File f2 = new File(outfilename);
		if(!f2.exists()) {//如果输出文件不存在，那么就创建一个新文件。
			f2.createNewFile();
		}
		
		
		
			FileReader fr = new FileReader(f1);
			
			FileWriter fw = new FileWriter(f2);
			
			BufferedReader bReader = new BufferedReader(fr);
			StringBuilder sb1 = new StringBuilder();//定义一个字符串缓存，将字符串存放缓存中
			
			String s1 = "";
			BufferedWriter bw = new BufferedWriter(fw);
			String hasRead;
			
			while((hasRead=bReader.readLine()) != null){
				sb1.append(hasRead);//将读取的字符串添加换行符后累加p存放在缓存中
//				bw.write(hasRead);
//				bw.newLine();
				
				} 
			String text = sb1.toString();
			String[] array = {".",",","?","!",":","‘","’","“","”","—",";","-"};
			for (int j = 0; j < array.length; j++) {
				text = text.replace(array[j]," ");                      //将text中的array数组中包含的特殊字符用空格代替
			}
			String[] textArray = text.split(" ");    
			
			char[] head = new char[10];
			char[] wei = new char[10];
			String[] danci = new String[textArray.length];
			for(int i = 0 ;i < textArray.length;i ++) {
				danci[i] = toLowerCase(textArray[i]);
			}
			for(int i = 0 ; i < danci.length;i++) {
				if(danci[i].length()==0) {
					System.out.println("input.txt中无单词");
					System.exit(0);
					
				}
				head[i] = danci[i].charAt(0);
				wei[i] = danci[i].charAt(danci[i].length()-1);
			}
			String[] fin = new String[10];
			for(int i = 0 ; i < wei.length; i ++) {
				StringBuilder sb2 = new StringBuilder();//定义一个字符串缓存，将字符串存放缓存中
				char c = wei[i];
				sb2.append(danci[i]+"+");
				for(int j = 0 ; j < head.length; j ++) {
					
					if(head[j] ==wei[i]) {
						wei[i] = wei[j];
						sb2.append(danci[j]+"+");
					}
				}
				String sb22 = sb2.toString();
				fin[i] = sb22;
				
				
			}
			
			int max = shuliang(fin[0]);
		    int n = 0;
			String maxf = fin[0];
			for(int i = 1 ;i < fin.length;i++) {
				
				n = shuliang(fin[i]);
				
				if(n>max) {
					maxf = fin[i];
				}
			}
			if(n==1) {
				System.out.println("无可连接单词");
				System.exit(0);
			}
			bw.write(maxf);
			bw.newLine();
			
			
			
			
			
			bw.flush();
			bReader.close();
			} catch (FileNotFoundException e){ 
				e.printStackTrace(); 
			} catch (IOException e) {
				e.printStackTrace();
				}
	} 
	public static void main(String args[]) throws IOException {
		Scanner scan = new Scanner(System.in);
		System.out.println("请输入两个文件名，以.txt结尾！");
		String file1 = scan.next();
		String file2 = scan.next();
		FileCaozuo(file1,file2);
		scan.close();

运行截图:

input.txt

output.txt