Mega Code Archive
Use RandomAccessFile to save an object
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import java.io.IOException;
import java.io.RandomAccessFile;
public class CreateEmployeeFile {
public static void main(String[] args) throws Exception {
String[] fnames = { "A", "B", "C" };
String[] lnames = { "a", "b", "c" };
String[] addresses = { "Box 100", "55 Street", "6 Lane" };
byte[] ages = { 46, 59, 32 };
double[] salaries = { 5.0, 6.0, 3.0 };
RandomAccessFile raf = new RandomAccessFile("employee.dat", "rw");
EmployeeRecord er = new EmployeeRecord();
for (int i = 0; i < fnames.length; i++) {
er.setFirstName(fnames[i]);
er.setLastName(lnames[i]);
er.setAddress(addresses[i]);
er.setAge(ages[i]);
er.setSalary(salaries[i]);
er.write(raf);
}
raf = new RandomAccessFile("employee.dat", "rw");
er = new EmployeeRecord();
int numRecords = (int) raf.length() / er.size();
for (int i = 0; i < numRecords; i++) {
er.read(raf);
System.out.print(er.getFirstName() + " ");
System.out.print(er.getLastName() + " ");
System.out.print(er.getAddress() + " ");
System.out.print(er.getAge() + " ");
System.out.println(er.getSalary());
}
raf.seek(0);
for (int i = 0; i < numRecords; i++) {
er.read(raf);
if (er.getAge() >= 55) {
er.setSalary(0.0);
raf.seek(raf.getFilePointer() - er.size());
er.write(raf);
raf.seek(raf.getFilePointer() - er.size());
er.read(raf);
}
System.out.print(er.getFirstName() + " ");
System.out.print(er.getLastName() + " ");
System.out.print(er.getAddress() + " ");
System.out.print(er.getAge() + " ");
System.out.println(er.getSalary());
}
}
}
class EmployeeRecord {
private String lastName;
private String firstName;
private String address;
private byte age;
private double salary;
void read(RandomAccessFile raf) throws IOException {
char[] temp = new char[15];
for (int i = 0; i < temp.length; i++)
temp[i] = raf.readChar();
lastName = new String(temp);
temp = new char[15];
for (int i = 0; i < temp.length; i++)
temp[i] = raf.readChar();
firstName = new String(temp);
temp = new char[30];
for (int i = 0; i < temp.length; i++)
temp[i] = raf.readChar();
address = new String(temp);
age = raf.readByte();
salary = raf.readDouble();
}
void write(RandomAccessFile raf) throws IOException {
StringBuffer sb;
if (lastName != null)
sb = new StringBuffer(lastName);
else
sb = new StringBuffer();
sb.setLength(15);
raf.writeChars(sb.toString());
if (firstName != null)
sb = new StringBuffer(firstName);
else
sb = new StringBuffer();
sb.setLength(15);
raf.writeChars(sb.toString());
if (address != null)
sb = new StringBuffer(address);
else
sb = new StringBuffer();
sb.setLength(30);
raf.writeChars(sb.toString());
raf.writeByte(age);
raf.writeDouble(salary);
}
void setAge(byte age) {
this.age = age;
}
byte getAge() {
return age;
}
void setAddress(String address) {
this.address = address;
}
String getAddress() {
return address;
}
void setFirstName(String firstName) {
this.firstName = firstName;
}
String getFirstName() {
return firstName;
}
void setLastName(String lastName) {
this.lastName = lastName;
}
String getLastName() {
return lastName;
}
void setSalary(double salary) {
this.salary = salary;
}
double getSalary() {
return salary;
}
int size() {
return 2 * (15 + 15 + 30) + 9;
}
}
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