Random File
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);
}
}
}
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