java编程大题

package 多线程;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileWriter;

public class ThreadDemo {
public int j;
public T1 t1;
public T2 t2;
public T3 t3;
public T4 t4;
ThreadDemo(){
j=1;
t1 = new T1();
t2 = new T2();
t3 = new T3();
t4 = new T4();
}

public class T1 implements Runnable{
public void run(){
j++;
System.out.println("T1: j="+j);
j++;
System.out.println("T1: j="+j);
}
}
public class T2 implements Runnable{
public void run(){
try {
FileWriter fw = new FileWriter("file.dat",true);
fw.write(j+"\r\n");
fw.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
System.out.println("File not found");
e.printStackTrace();
}
catch(Exception e){
e.printStackTrace();
}
System.out.println("T2: write j to file.dat, j="+j);
}
}
public class T3 implements Runnable{
public void run(){
j--;
System.out.println("T3: j="+j);
}
}
public class T4 implements Runnable{
public void run(){
String temp="";
String result="";
boolean flag = true;
System.out.println("T4: 删除j="+j+"的数据");
try{
FileWriter fw = new FileWriter("temp.dat");

DataInputStream dis = new DataInputStream(
new BufferedInputStream(
new FileInputStream("file.dat")));

while( (temp = dis.readLine() )!=null){
if(  temp.equals(String.valueOf(j) ) ){
System.out.println("删除"+j);
}else{
fw.write(temp+"\r\n");
System.out.println("复制"+String.valueOf(temp)+"到temp.dat");
}
}
fw.close();
dis.close();
}catch(EOFException eof){
System.out.println("文件读取结束");
}catch(NullPointerException npe){
npe.printStackTrace();
}catch(Exception e){
System.out.println("其他错误");
}

File f1 = new File("file.dat");
File f2 = new File("temp.dat");
f1.delete();
f2.renameTo(f1);

}
}
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
ThreadDemo td = new ThreadDemo();

td.t1.run();
td.t2.run();
td.t3.run();
td.t4.run();

}

}