ObjectInputStream

In this chapter you will learn:

Use ObjectInputStream

The ObjectInput interface extends the DataInput interface.

The ObjectInputStream class extends the
InputStream class and implements the ObjectInput
interface.
ObjectInputStream is responsible for reading objects from a stream.

ObjectInputStream supports object serialization through
the readObject( ) method.
readObject( ) method is called to deserialize an object.

A constructor of this class is

• ObjectInputStream(InputStream inStream) throws IOException
inStream is the input stream from which serialized objects should be read.

Read through ObjectOutputStream

The following code show to use ObjectOutputStream
to read and write primitive data.

import
 java.io.BufferedInputStream;
import
 java.io.BufferedOutputStream;
import
 java.io.EOFException;
import
 java.io.FileInputStream;
import
 java.io.FileOutputStream;
import
 java.io.IOException;
import
 java.io.ObjectInputStream;
import
 java.io.ObjectOutputStream;
import
 java.math.BigInteger;
/
*
 
 
j
 
a
 
v
a
2
s
.
c
 
o
 
 
m
*
/
public
 
class
 Main {
  
static
 
final
 String dataFile = 
"data.dat"
;

  
public
 
static
 
void
 main(String[] args) 
throws
 IOException, ClassNotFoundException {

    ObjectOutputStream out = null;
    
try
 {
      out = 
new
 ObjectOutputStream(
new
 BufferedOutputStream(
new
 FileOutputStream(dataFile)));

      out.writeObject(
new
 BigInteger(
"123"
));
      out.writeInt(123);
      out.writeUTF(
"a String"
);
    } 
finally
 {
      out.close();
    }

    ObjectInputStream in = null;
    
try
 {
      in = 
new
 ObjectInputStream(
new
 BufferedInputStream(
new
 FileInputStream(dataFile)));
      
try
 {
        
while
 (true) {
          BigInteger price = (BigInteger) in.readObject();
          
int
 unit = in.readInt();
          String desc = in.readUTF();
          System.out.println(price);
          System.out.println(unit);
          System.out.println(desc);
        }
      } 
catch
 (EOFException e) {
      }

    } 
finally
 {
      in.close();
    }
  }
}

The output:

Read object

The following code shows how to use the ObjectInputStream and
ObjectOutputStream to do the object serialization.

import
 java.io.FileInputStream;
import
 java.io.FileOutputStream;
import
 java.io.ObjectInputStream;
import
 java.io.ObjectOutputStream;
import
 java.io.Serializable;
/
/
f
r
o
m
 
j
a
 
 
v
a
 
2
s
.
 
c
 
 
o
m
public
 
class
 Main {
  
public
 
static
 
void
 main(String args[]) 
throws
 Exception{
      MyClass object1 = 
new
 MyClass(
"Hello"
, -1, 2.1);
      System.out.println(
"object1: "
 + object1);
      FileOutputStream fos = 
new
 FileOutputStream(
"serial"
);
      ObjectOutputStream oos = 
new
 ObjectOutputStream(fos);
      oos.writeObject(object1);
      oos.flush();
      oos.close();

      FileInputStream fis = 
new
 FileInputStream(
"serial"
);
      ObjectInputStream ois = 
new
 ObjectInputStream(fis);
      MyClass object2 = (MyClass) ois.readObject();
      ois.close();
      System.out.println(
"object2: "
 + object2);
  }
}

class
 MyClass 
implements
 Serializable {
  String s;
  
int
 i;
  
double
 d;

  
public
 MyClass(String s, 
int
 i, 
double
 d) {
    this.s = s;
    this.i = i;
    this.d = d;
  }

  
public
 String toString() {
    
return
 
"s="
 + s + 
"; i="
 + i + 
"; d="
 + d;
  }
}

Next chapter…

What you will learn in the next chapter: