Unlocking the Power of Java: Understanding ObjectInputStream
Getting Started with ObjectInputStream
When working with Java, understanding the ObjectInputStream class is crucial for reading objects that were previously written by ObjectOutputStream. As a subclass of the InputStream abstract class, ObjectInputStream plays a vital role in the serialization and deserialization process.
How ObjectInputStream Works
The primary function of ObjectInputStream is to read data written by ObjectOutputStream. This process involves converting Java objects into corresponding streams, known as serialization. These streams can be stored in files or transferred through networks. When we need to read these objects, ObjectInputStream comes into play, converting the streams back into their original object form, a process known as deserialization.
Creating an ObjectInputStream
To create an ObjectInputStream, we must first import the java.io.ObjectInputStream package. Then, we can create an input stream linked to a file stream, enabling us to read objects from the file.
Methods of ObjectInputStream
The ObjectInputStream class provides implementations of various methods inherited from the InputStream class. Some of the key methods include:
- read(): reads a byte of data from the input stream
- readBoolean(): reads data in boolean form
- readChar(): reads data in character form
- readInt(): reads data in integer form
- readObject(): reads the object from the input stream
Practical Examples
Let’s explore two examples that demonstrate the power of ObjectInputStream:
Example 1: Reading Objects from a File
In this example, we use the readInt() and readObject() methods to read integer data and object data from a file. We first write data to the file using ObjectOutputStream and then read it using ObjectInputStream.
Example 2: Reading and Writing Objects
In this example, we create an ObjectOutputStream named output using a FileOutputStream named file, and an ObjectInputStream named input using a FileInputStream named fileStream. We then write an object of the Dog class to the file using ObjectOutputStream and read it back using ObjectInputStream.
Important Note
Remember that the ObjectOutputStream only writes serializable objects to the output stream. Therefore, the Dog class must implement the Serializable interface.
Exploring Further
To learn more about the ObjectInputStream class and its methods, visit the official Java documentation. Additionally, explore the Java InputStream Class and Java OutputStream Class for a deeper understanding of Java’s input/output streams.