一笔试小题---文件读写操作（希望对刚毕业找工作的朋友有所帮助）

我也来发表个，呵呵

package cn.xbmu.lib.jfly.test;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileNotFoundException;

import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;

/**
 * 文件intel.txt,内容如下：
 * 小王【空格】10000【回车】
 * 小强【空格】12345【回车】
 * 小张【空格】2342 【回车】
 * 小强【空格】1030 【回车】
 * 小周【空格】1020 【回车】
 * 小杨【空格】2342 【回车】
 * 请编写一程序从test.txt中读取数据，并按数字大小排序后写入另一文件sun.txt(写入格式同上)
 * @author JFly
 */
public class SortFileContentByNum {

    public static void main(String[] args) throws FileNotFoundException, IOException {
        BufferedReader br = new BufferedReader(new FileReader("C:/test.txt"));
        String line = null;
        int size = 0;
        ArrayList<String> al = new ArrayList<String>();
        while ((line = br.readLine()) != null) {
            if (!line.isEmpty()) {
                al.add(line);
                size++;
            }
        }
        br.close();
        
        String[] b = al.toArray(new String[size]);
        Arrays.sort(b, new Comparator<String>() {
             public int compare(String s1, String s2) {
                int i1 = 0;
                int i2 = 0;
                if (s1.matches(".+\\s+\\d+") && s2.matches(".+\\s+\\d+")) {
                    i1 = Integer.parseInt(s1.replaceAll("\\D", ""));
                    i2 = Integer.parseInt(s2.replaceAll("\\D", ""));
                }
                if(i1 == i2) {
                    String str1 = s1.replaceAll("\\d", "");
                    String str2 = s2.replaceAll("\\d", "");
                    return str1.compareTo(str2) > 0 ? -1 : 1;
                }
                return i1 < i2 ? -1 : 1;
            }
        });
                
        BufferedWriter bw = new BufferedWriter(new FileWriter("c:/result.txt"));
         for(String s : b) {
            bw.write(s);
            bw.write("\r");
        }
        bw.flush();
        bw.close();
    }
}

public class TestSort {
	public static void main(String[] args) {
		List<Integer> intList = new ArrayList<Integer>();
		intList.add(123);
		intList.add(122223);
		intList.add(1233);
		intList.add(1234);
		intList.add(125);

		Integer[] intArr = intList.toArray(new Integer[intList.size()]);
		Arrays.sort(intArr);

		for (int i : intArr) {
			System.out.println(i);
		}
	}
}

java.util.Collections.sort(intList);

import com.j2se.file.MyIntComparator;//自定义比较器
import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Iterator;
import java.util.TreeMap;


/***
*读文件test.txt内容（文件内容格式： 小王【空格】10000【回车】
*                                小强【空格】12345【回车】
*并对该文件内容按存款数排序，然后将其写入另一文件内
*
*****/
public class fileSort {

/*****
* 以行为单位读写文件
            *@param fileName  源文件
            *@param toFileName  目标文件
* ****/
public static void  read_writeFile(String fileName,String toFileName){
File file = new File(fileName);
BufferedReader reader=null;
TreeMap<Integer,String> map = new TreeMap<Integer,String>(new MyIntComparator());
File toFile = new File(toFileName);
PrintWriter writer = null;
try{
System.out.println("------------------读文件开始-------------------------------");
System.out.println();
System.out.println("以行为单位读取文件内容，每次读取一整行");
reader = new BufferedReader(new FileReader(file));
String tempString = null;
String[] ss = null;
int line = 1;

//一次读一行，直到读取为null
while((tempString = reader.readLine()) != null){
//显示行号
System.out.println("line number is "+line+"::"+tempString);
line++;

ss = tempString.split(" ");
int i = 0;
String value = ss[i];
int key =Integer.parseInt(ss[i+1]);
System.out.println("key is:"+key);
System.out.println("value is:"+value);
map.put(key, value);

}
System.out.println("------------------读文件结束-------------------------------");
System.out.println();
System.out.println("------------------写文件开始-------------------------------");
System.out.println("写文件开始："+file.getAbsolutePath());
writer = new PrintWriter(new FileOutputStream(toFile));
if(map !=null){
Object key = null;
Object value = null;
// 使用迭代器遍历Map的键，根据键取值
Iterator it = map.keySet().iterator();
while (it.hasNext()){
key = it.next();
value = map.get(key);
System.out.println("key is :"+key);
System.out.println("vlaue is :"+value);
//能写各种基本类型数据
writer.print(value+" ");
writer.print(key+" ");
//换行
writer.println();
//写入文件
writer.flush();
}

System.out.println("写文件"+file.getAbsolutePath()+"成功！");
System.out.println("---------------------------写文件结束--------------------------");
}
}catch(IOException e){
e.printStackTrace();
}finally{
if(reader != null){
try{
reader.close();
}catch(IOException e1){
e1.printStackTrace();
}
}
if(writer !=null){
writer.close();
}
}

}

public static void main(String[] args){
String fileName = "D:/test.txt";
String toFileName = "D:/test1.txt";
fileSort.read_writeFile(fileName, toFileName);
}
}

----------------自定义比较器--------------------------------------
import java.util.Comparator;

/**
* 整数比较器，将整数按降序排列
*/
class MyIntComparator implements Comparator{

/**
* o1比o2大，返回-1；o1比o2小，返回1。
*/
public int compare(Object o1, Object o2) {
int i1 = ((Integer)o1).intValue();
int i2 = ((Integer)o2).intValue();
if (i1 < i2){
return 1;
}
if (i1 > i2){
return -1;
}
return 0;
}
} 

package com.saturday;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class ReadTxt {
	public static void main(String args[]){
		try{			
			List lsRecords=readData("D:/Data.txt");
			sortRecord(lsRecords,"asc");
			writeData(lsRecords);
		}catch(FileNotFoundException ex){
			System.out.println("无法读取数据文件!");
		}catch(Exception ex){
			System.out.println(ex.getMessage());
		}
	}
	
	public static List readData(String sFilePath) throws Exception{
		BufferedReader bufreader=null;
		List lsRecords=new ArrayList();
		
		try{
			StringBuffer sbData=new StringBuffer();
			String sLineData=null;
			bufreader=new BufferedReader(new FileReader(sFilePath));
			Pattern p=Pattern.compile(
				"^\\s*(.*?)\\s+(\\d+)\\s*$",
				Pattern.MULTILINE);
			
			while((sLineData=bufreader.readLine())!=null){
				sbData.append(sLineData+"\n");
			}
			
			Matcher m=p.matcher(sbData);
			while(m.find()){
				lsRecords.add(m.group(1)+":"+m.group(2));				
			}
		}catch(Exception ex){
			throw ex;
		}finally{
			try{
				if(bufreader!=null)
					bufreader.close();
			}catch(Exception ex){}
		}
		
		return lsRecords;
	}
	
	public static void sortRecord(List lsRecords,String sSortSty){
		Comparator AscCmp=new Comparator(){
			public int compare(Object o1,Object o2){
				String str1=(String)o1;
				String str2=(String)o2;
				int int1=Integer.parseInt(
					str1.substring(str1.indexOf(':')+1));
				int int2=Integer.parseInt(
					str2.substring(str2.indexOf(':')+1));
								
				return int1<int2?-1:1;
			}	
		};
		
		Comparator DesCmp=new Comparator(){
			public int compare(Object o1,Object o2){
				String str1=(String)o1;
				String str2=(String)o2;
				int int1=Integer.parseInt(
					str1.substring(str1.indexOf(':')+1));
				int int2=Integer.parseInt(
					str2.substring(str2.indexOf(':')+1));
								
				return int1<int2?1:-1;
			}	
		};		
		
		if(sSortSty.equals("des"))
			Collections.sort(lsRecords,DesCmp);	
		else
			Collections.sort(lsRecords,AscCmp);	
	}
	
	public static void writeData(List lsRecords) throws Exception{
		BufferedWriter bufwriter=null;
		
		try{
			bufwriter=new BufferedWriter(new FileWriter("D:/SortedData.txt"));
			String sLineData=null;
			
			Iterator i=lsRecords.iterator();
			while(i.hasNext()){
				sLineData=(String)i.next();
				sLineData=sLineData.replaceAll(":", "  ")+"\n";
				bufwriter.write(sLineData);
			}	
		}catch(Exception ex){
			throw ex;
		}finally{	
			try{
				if(bufwriter!=null)
					bufwriter.close();
			}catch(Exception ex){}			
		}
	}
}