You should Make Entry
a Serializable
class and use Serialization
to save the array of Entry
objects
in a file and deserialization
to get the array of objects back from the stream of bytes saved on file. For Example, consider the code given below . Here Person
is a class which implements java.io.Serializable
marker interface
. Within main body of SerializeArray
an array of Person
is created and it is saved in a file named Persons.ser
(You can use any name here for the file) using saveArray
. This array is then read back from the file using loadArray
.
import java.io.*;
class Person implements Serializable //Make Person class Serializable so that its objects can be serialized.
{
private static final long SerialVersionUID = 20L;
String name;
int age;
public Person(String name,int age)
{
this.name = name;
this.age = age;
}
public String toString()
{
return "Name:"+name+", Age:"+age;
}
}
public class SerializeArray
{
public static void saveArray(Person[] arr)throws Exception //writes the array of Person to a file "Persons.ser"
{
ObjectOutputStream os = new ObjectOutputStream(new FileOutputStream("Persons.ser"));
os.writeObject(arr);
os.close();
}
public static Person[] loadArray()throws Exception //Reads the array of Persons back from file.
{
ObjectInputStream oin = new ObjectInputStream(new FileInputStream("Persons.ser"));
Person[] arr = (Person[]) oin.readObject();
oin.close();
return arr;
}
public static void main(String[] args) throws Exception
{
Person[] arr= new Person[3];
for (int i = 0 ; i < arr.length ; i++)
{
arr[i] = new Person("Person"+i,25+i);
}
System.out.println("Saving array to file");
saveArray(arr);
System.out.println("Reading array back from file");
Person[] per = loadArray();
for (Person p : per)
{
System.out.println(p);
}
}
}
UPDATE
To incorporate this concept in your program you should first change your Entry class declaration as something like this:
public class Entry implements java.io.Serializable
And then change your doSave()
method as follows:
public void doSave() throws Exception {
ObjectOutputStream os = new ObjectOutputStream(new FileOutputStream("contacts.txt"));
os.writeObject(entryList);
os.close();
}
And then change your doLoad()
method as follows:
public void doLoad() throws Exception {
if (length != 0) {
//throw new Exception ("I'm not empty");
//File c = new File ("contacts.txt");//No need to access the File here..
Scanner input = new Scanner(c);
while (input.hasNextLine()) {
Entry e = new Entry();
e.name = input.next();
if ("q".equalsIgnorecase(e.name))
break;
e.number = input.next();
e.notes = input.next();
doAddEntry(e);
}
doAddEntry(null);
}
}
And change your doAddEntry
method as follows:
public void doAddEntry(Entry entry) throws Exception {
if (entry == null)
{
//save file here..
doSave();
}
else if (length == 200) {
//save file here..
doSave();
throw new Exception("I'm full");
}
else
{
boolean matched = false;
for (int i = 0; i<length; i++) {
if (entryList[i].name.compareToIgnoreCase(entry.name) == 0) {
matched = true;
break;
}
if(!matched)
{
entryList[entryList.length] = entry;
}
}
}
}