Reference no: EM13725393
You will handle student records in a file named "student_record". Each record in the file consists of student number of integer type and student name of 32 characters, so the size of each record is 36 bytes. You need to write a Java program to store the following four records into the file:
72 James
56 Mark
87 John
30 Phillip
44 Andrew
Then, the program sorts the records in the file using any simple sorting algorithm such as bubble sorting, with the first field - student number, and prints all records in the file after sorting. When the program sorts the student records, the program should not read all records in memory at once. The program should move records in the file. For example, after the program reads the first two records, it may switch the records (because 72 > 56) and write them in the same position in the file.
You need to submit Java programs and screen shots that show how your programs work.
Manipulating Files in Java
The following sections are prepared to help you understand how to manipulate files in Java application programs.
1. File
• Basic idea to use files
o Open - in Java, create an object for the given file
o Read; write
o Close
• Sequential access
• Random access
o Just keep reading or writing
o Read or write any place in a file
2. Sequential access
2.1 Writing
import java.io.*;
classFileWriteStreamTest {
public static void main (String[] args) {
FileWriteStreamTest f = new FileWriteStreamTest();
f.writeMyFile();
}
voidwriteMyFile() {
DataOutputStream dos = null;
String record = null;
intrecCount = 0;
try {
File f = new File("mydata.txt");
if (!f.exists())
f.createNewFile();
FileOutputStreamfos = new FileOutputStream(f);
BufferedOutputStreambos = new BufferedOutputStream(fos);
dos = new DataOutputStream(bos);
dos.writeBytes("Test\n");
dos.writeBytes("Welcome\n");
dos.writeBytes("Operating System\n");
dos.writeBytes("File System\n");
} catch (IOException e) {
System.out.println("Uh oh, got an IOException error!" +
} finally {
// if the file opened okay, make sure we close it
if (dos != null) {
try { dos.close(); }
catch (IOExceptionioe) { }
}
import java.io.*;
classFileReadStreamTest {
public static void main (String[] args) {
FileReadStreamTest f = new FileReadStreamTest();
f.readMyFile();
voidreadMyFile() {
DataInputStream dis = null;
String record = null;
intrecCount = 0;
File f = new File("mydata.txt");
if (!f.exists()) {
System.out.println(f.getName() + " does not exist");
return;
}
FileInputStreamfis = new FileInputStream(f);
BufferedInputStreambis = new BufferedInputStream(fis);
dis = new DataInputStream(bis);
while ( (record=dis.readLine()) != null ) {
recCount++;
System.out.println(recCount + ": " + record);
}
} catch (IOException e) {
System.out.println("Uh oh, got an IOException error!" +
} finally {
// if the file opened okay, make sure we close it
if (dis != null) {
try { dis.close(); }
catch (IOExceptionioe) { }
}
classFileRandomAccessTest {
public static void main (String[] args) {
FileRandomAccessTest f = new FileRandomAccessTest();
f.readWriteMyFile();
voidreadWriteMyFile() {
RandomAccessFileraf = null;
String s = null;
File f = new File("mydata.txt");
if (!f.exists()) // check if the file exists
f.createNewFile(); // create a new file
raf = new RandomAccessFile(f, "rw"); // open a file for random
access with "r", "rw"
if (raf.length() > 7) { // the size of the file
raf.seek(7); // move the file pointer
System.out.println(raf.readLine()); // read a line fromthe file pointer
file pointer
s = raf.readLine();
System.out.println(s);
raf.seek(raf.getFilePointer() - s.length()); // get the
raf.writeBytes("Test RamdomAccessFile\n"); // write bytes
}
} catch (IOException e) {
System.out.println("Uh oh, got an IOException error!" +
e.getMessage());
} finally {
// if the file opened okay, make sure we close it
if (raf != null) {
try { raf.close(); } // close the file
catch (IOExceptionioe) { }
}
}
}