第二阶段

package word_show;

import java.io.*;
import java.util.*;
import java.util.Map.Entry;

public class word2 {
public static int n=0;
public static void main(String[] args) {
Scanner input=new Scanner(System.in);
String s;
int count=0;
int num=1;
//FileReader读取文件
String file1="D:\\QQ Download\\java\\piao_english.txt";
//FileWriter写入文件
String file2="D:\\QQ Download\\java\\max_num.txt";
try
{
BufferedReader a=new BufferedReader(new FileReader(file1));
BufferedWriter b=new BufferedWriter(new FileWriter(file2));
StringBuffer c=new StringBuffer();
//将文件内容存入StringBuffer中
while((s = a.readLine()) != null)
{
//用于拼接字符串
c.append(s);
}
//将StringBuffer转换成String，然后再将所有字符转化成小写字符
String m=c.toString().toLowerCase();
//匹配由数字和26个字母组成的字符串
String [] d=m.split("[^a-zA-Z0-9]+");
//遍历数组将其存入Map<String, Integer>中
Map<String , Integer> myTreeMap=new TreeMap<String, Integer>();
for(int i = 0; i < d.length; i++) {
//containsKey()方法用于检查特定键是否在TreeMap中映射
if(myTreeMap.containsKey(d[i])) {
count = myTreeMap.get(d[i]);
myTreeMap.put(d[i], count + 1);
}
else {
myTreeMap.put(d[i], 1);
}
}
//通过比较器实现排序
List<Map.Entry<String, Integer>> list = new ArrayList<Map.Entry<String, Integer>>(myTreeMap.entrySet());
//按降序排序
Collections.sort(list, new Comparator<Map.Entry<String, Integer>>() {

public int compare(Entry<String, Integer> k1, Entry<String, Integer> k2) {
//返回两个单词出现次数较多的那个单词的出现次数
return k2.getValue().compareTo(k1.getValue());
}

});
System.out.println("请输入需要输出的数量最多的前N名的N:");
n=input.nextInt();
for(Map.Entry<String, Integer> map : list) {
if(num <= n) {
//按内容输出到指定文件中去
b.write("出现次数第" + num + "的单词为：" + map.getKey() + "，出现频率为" + map.getValue() + "次");
b.newLine();
System.out.println(map.getKey() + ":" + map.getValue());
num++;
}
else break;
}
a.close();
b.close();
}
catch(FileNotFoundException e)
{
System.out.println("找不到指定文件");
}
catch(IOException e)
{
System.out.println("文件读取错误");
}
System.out.println("输出完成");
}
}