新手，带有正则表达式的代码运行到没有反应了

import java.io.BufferedReader;import java.io.BufferedWriter;import java.io.File;import java.io.FileReader;import java.io.FileNotFoundException;import java.io.FileWriter;import java.io.IOException;import java.lang.Exception;import java.util.regex.*;public class pattern {    public static void main(String[] args) {            File f111 = new File("F:/JAVA代码存储/文件提取汉字/111.txt");            File f222 = new File("F:/JAVA代码存储/文件提取汉字/222.txt");            try{        BufferedReader reader=new BufferedReader(new FileReader(f111)); //缓冲流        StringBuilder sb=new StringBuilder();      //将所有源码按格式读入sb中        StringBuilder sb2=new StringBuilder();      //将所有匹配出的源码按格式写入sb2中            BufferedWriter bw=new BufferedWriter(new FileWriter(f222)); //缓冲流        String str,str2;      //负责读每一行源码        while((str=reader.readLine())!=null)        {            str=str+"\n";            sb.append(str);        }            String reg = "[\u4e00-\u9fa5](.|[\u4e00-\u9fa5])*。";                Pattern pat = Pattern.compile(reg);        System.out.println(0);        Matcher mat = pat.matcher(sb.toString());        System.out.println(mat.find());        if(mat.find()==false)        {System.out.println("没有匹配到");}        if(mat.find()==true)        {System.out.println("匹配到");}        System.out.println(1);        while(mat.find())        {            str2 = mat.group();                        if(str2.length()<1)                continue;            System.out.println(str2);            str2 = str2+"\n";            sb2.append(str2);        }        System.out.println(2);        String sbb;        sbb = sb2.toString();                bw.write(sbb);        reader.close();            bw.close();    }    catch(FileNotFoundException e1){}catch(IOException e2){}    catch(PatternSyntaxException e3){System.out.println("语法错误");}        System.out.println("完成");    }}