DataInputStream Class in Java

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Introduction

The DataInputStream class is a filter stream that reads data from an input stream in a binary format. This class is essential for reading primitive data types (such as int, float, double, etc.) from a stream in a way that ensures the data is interpreted correctly regardless of the platform. By providing methods to read Java's primitive data types, DataInputStream makes it easier to handle binary I/O operations.

Table of Contents

1. Creating a DataInputStream
2. Reading Data from a DataInputStream
3. Closing the Stream
4. Complete Example
5. Conclusion

Creating a DataInputStream

To create a DataInputStream, you need to wrap it around another input stream, such as a FileInputStream. This enables you to read data from a file or another input source in a binary format.

Example

import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;

public class DataInputStreamExample {
    public static void main(String[] args) {
        try {
            // Creating DataInputStream using FileInputStream
            FileInputStream fis = new FileInputStream("example.dat");
            DataInputStream dis = new DataInputStream(fis);

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }
}

In the example above, DataInputStream is created using a FileInputStream to read from a file named example.dat.

Reading Data from a DataInputStream

The DataInputStream class provides several methods to read primitive data types from the input stream:

• boolean readBoolean(): Reads a boolean value.
• byte readByte(): Reads an 8-bit byte.
• char readChar(): Reads a 16-bit character.
• double readDouble(): Reads a 64-bit double.
• float readFloat(): Reads a 32-bit float.
• int readInt(): Reads a 32-bit integer.
• long readLong(): Reads a 64-bit long.
• short readShort(): Reads a 16-bit short.

Example

import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.IOException;

public class DataInputStreamReadExample {
    public static void main(String[] args) {
        try (DataInputStream dis = new DataInputStream(new FileInputStream("example.dat"))) {
            int intValue = dis.readInt();
            double doubleValue = dis.readDouble();
            boolean booleanValue = dis.readBoolean();

            System.out.println("Integer Value: " + intValue);
            System.out.println("Double Value: " + doubleValue);
            System.out.println("Boolean Value: " + booleanValue);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

In the example above, DataInputStream reads data from a file named example.dat. The file is expected to contain an integer, a double, and a boolean value in sequence.

Closing the Stream

It is important to close the DataInputStream after completing the I/O operations to release the system resources associated with the stream. This can be done using the close() method.

Example

import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.IOException;

public class DataInputStreamCloseExample {
    public static void main(String[] args) {
        DataInputStream dis = null;
        try {
            dis = new DataInputStream(new FileInputStream("example.dat"));
            int intValue = dis.readInt();
            double doubleValue = dis.readDouble();
            boolean booleanValue = dis.readBoolean();

            System.out.println("Integer Value: " + intValue);
            System.out.println("Double Value: " + doubleValue);
            System.out.println("Boolean Value: " + booleanValue);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (dis != null) {
                    dis.close();
                }
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
    }
}

In the example above, the DataInputStream is closed in the finally block to ensure that it is closed even if an exception occurs.

Alternatively, you can use the try-with-resources statement, which ensures that the stream is closed automatically.

Example

import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.IOException;

public class DataInputStreamTryWithResourcesExample {
    public static void main(String[] args) {
        try (DataInputStream dis = new DataInputStream(new FileInputStream("example.dat"))) {
            int intValue = dis.readInt();
            double doubleValue = dis.readDouble();
            boolean booleanValue = dis.readBoolean();

            System.out.println("Integer Value: " + intValue);
            System.out.println("Double Value: " + doubleValue);
            System.out.println("Boolean Value: " + booleanValue);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

In the example above, the try-with-resources statement is used to automatically close the DataInputStream.

Complete Example

Here is a complete example demonstrating the creation, reading, and closing of a DataInputStream.

DataInputStreamExample.java

import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.IOException;

public class DataInputStreamExample {
    public static void main(String[] args) {
        try (DataInputStream dis = new DataInputStream(new FileInputStream("example.dat"))) {
            int intValue = dis.readInt();
            double doubleValue = dis.readDouble();
            boolean booleanValue = dis.readBoolean();

            System.out.println("Integer Value: " + intValue);
            System.out.println("Double Value: " + doubleValue);
            System.out.println("Boolean Value: " + booleanValue);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

In this example, a DataInputStream is created, data is read from a file, and the stream is automatically closed using the try-with-resources statement.

Conclusion

The DataInputStream class in Java is used for reading primitive data types from an input stream in a machine-independent way. By understanding how to create, read, and close a DataInputStream, you can effectively handle binary I/O operations in your Java applications. Remember to always close the stream after use to ensure that system resources are properly released.