Java ObjectInputStream readObject() Method

The readObject() method of ObjectInputStream class is used to read an object from the objectinputstream. It reads the class of the object, the signature of the class, static, non-static fields and supertype.

Syntax

Parameter

Returns

The object read from the stream.

Throws

ClassNotFoundException

InvalidClassException

StreamCorruptedException

OptionalDataException

IOException

Example 1

import java.io.*;
import static java.lang.System.out;

public class ObjectInputStreamreadObjectExample1 {
   public static void main(String[] args) {
      try {
          String str1 = "JavaTpoint";
          FileOutputStream outstream = new FileOutputStream("file1.txt");
          ObjectOutputStream objoutstream = new ObjectOutputStream(outstream);
          objoutstream.writeObject(new WorkClass());
          objoutstream.writeObject(str1);
          objoutstream.flush();
          ObjectInputStream objinstream = new ObjectInputStream(new FileInputStream("file1.txt"));
          WorkClass  obj = (WorkClass) objinstream.readObject();
          System.out.println("String in Serializable Class   : " + obj.str);
          System.out.println("String in MainClass  :  " +str1);
      } catch (Exception ex) {
         ex.printStackTrace();
      }
   }

   static class WorkClass implements Serializable {
      String str = "Welcome to javaTpoint";
      private String readObject(ObjectInputStream objin) 
         throws IOException, ClassNotFoundException {
         ObjectInputStream.GetField g = objin.readFields();
         return (String) g.get("str", null);
      }
   }
}

Output:

String in Serializable Class   : Welcome to javaTpoint
String in MainClass  :  JavaTpoint

Example 2

package ObjectInputStream;

import java.io.*;
import java.io.ObjectInputStream;

public class ObjectInputStreamreadObjectExample2   {
   public static void main(String[] args) {
      try {
          FileOutputStream outstream = new FileOutputStream("file1.txt");
          ObjectOutputStream objoutstream = new ObjectOutputStream(outstream);
          FileInputStream instream = new FileInputStream("file2.txt");
          ObjectInputStream objinstream = new ObjectInputStream(instream);
          String str=objinstream.toString();
          objoutstream.writeObject(new WorkClass());
          objoutstream.writeObject(str);
          objoutstream.flush();
         ObjectInputStream objinputstram = new ObjectInputStream(new FileInputStream("file1.txt"));
         //read the object from object input stream and cast it to String type.
         System.out.println("" + (String) objinstream.readObject());
          //read the object from object input stream and cast it to workclass typr.
         WorkClass obj1 = (WorkClass) objinputstram.readObject();
         System.out.println("string  in Work class  : " + obj1.str1);
      } catch (Exception ex) {
         ex.printStackTrace();
      }
   }
   static class WorkClass implements Serializable {
      String str1 = "javaTpoint";
      private void readObject(ObjectInputStream objin)
         throws IOException, ClassNotFoundException {
         objin.defaultReadObject();
      }
   }
}

Output:

java.io.ObjectInputStream@1b28cdfa
string  in Work class  : javaTpoint

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