RandomFileTest.java Source code

Introduction

Here is the source code for RandomFileTest.java

Source

import java.io.DataInput;
import java.io.DataOutput;
import java.io.DataOutputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.RandomAccessFile;

public class RandomFileTest {
    public static void main(String[] args) {
        Employee[] staff = new Employee[3];

        staff[0] = new Employee("Harry Hacker", 35000);
        staff[1] = new Employee("Carl Cracker", 75000);
        staff[2] = new Employee("Tony Tester", 38000);
        try {
            DataOutputStream out = new DataOutputStream(new FileOutputStream("employee.dat"));
            for (int i = 0; i < staff.length; i++)
                staff[i].writeData(out);
            out.close();
        } catch (IOException e) {
            System.out.print("Error: " + e);
            System.exit(1);
        }

        try {
            RandomAccessFile in = new RandomAccessFile("employee.dat", "r");
            int count = (int) (in.length() / Employee.RECORD_SIZE);
            Employee[] newStaff = new Employee[count];

            for (int i = count - 1; i >= 0; i--) {
                newStaff[i] = new Employee();
                in.seek(i * Employee.RECORD_SIZE);
                newStaff[i].readData(in);
            }
            for (int i = 0; i < newStaff.length; i++)
                newStaff[i].print();
        } catch (IOException e) {
            System.out.print("Error: " + e);
            System.exit(1);
        }
    }
}

class Employee {
    public static final int NAME_SIZE = 40;

    public static final int RECORD_SIZE = 2 * NAME_SIZE + 8 + 4 + 4 + 4;

    private String name;

    private double salary;

    public Employee(String n, double s) {
        name = n;
        salary = s;
    }

    public Employee() {
    }

    public void print() {
        System.out.println(name + " " + salary);
    }

    public void writeData(DataOutput out) throws IOException {
        DataIO.writeFixedString(name, NAME_SIZE, out);
        out.writeDouble(salary);
    }

    public void readData(DataInput in) throws IOException {
        name = DataIO.readFixedString(NAME_SIZE, in);
        salary = in.readDouble();
    }
}

class DataIO {
    public static String readFixedString(int size, DataInput dataInput) throws IOException {
        StringBuffer strBuffer = new StringBuffer(size);
        int count = 0;
        boolean more = true;
        while (more && count < size) {
            char aChar = dataInput.readChar();
            count++;
            if (aChar == 0)
                more = false;
            else
                strBuffer.append(aChar);
        }
        dataInput.skipBytes(2 * (size - count));
        return strBuffer.toString();
    }

    public static void writeFixedString(String str, int size, DataOutput dataOutput) throws IOException {

        for (int i = 0; i < size; i++) {
            char aChar = 0;
            if (i < str.length())
                aChar = str.charAt(i);
            dataOutput.writeChar(aChar);
        }
    }
}