Java - ObjectStreamField Class

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Introduction

The Java ObjectStreamField class is a description of a Serializable field from a Serializable class. An array of ObjectStreamFields is used to declare the Serializable fields of a class.

Class declaration

Following is the declaration for Java.io.ObjectStreamField class −

 public class ObjectStreamField extends Object implements Comparable<Object> 

Class constructors

Class methods

Methods inherited

This class inherits methods from the following classes −

• Java.io.Object

Example - Writing to a file using FileOutputStream and closing it

The following example shows the usage of OutputStream close() method. We're writing data to a file, then explicitly close the stream.

OutputStreamDemo.java

 package com.tutorialspoint; import java.io.FileOutputStream; import java.io.IOException; import java.io.OutputStream; public class OutputStreamDemo { public static void main(String[] args) { OutputStream os = null; try { os = new FileOutputStream("example1.txt"); String data = "Hello, OutputStream!"; os.write(data.getBytes()); System.out.println("Data written to file."); } catch (IOException e) { e.printStackTrace(); } finally { try { if (os != null) { os.close(); // important to close the stream System.out.println("Stream closed."); } } catch (IOException e) { e.printStackTrace(); } } } } 

Output

Let us compile and run the above program, this will produce the following result−

 Data written to file. Stream closed. 

Explanation

• os.close() ensures the file is properly saved and the resource is released.

• Not closing could lead to data not being written or file locks.

Example - Using flush() with FileOutputStream

The following example shows the usage of OutputStream flush() method.

OutputStreamDemo.java

 package com.tutorialspoint; import java.io.FileOutputStream; import java.io.IOException; public class OutputStreamDemo { public static void main(String[] args) { try { FileOutputStream fos = new FileOutputStream("example1.txt"); String data = "Hello, this is a flush example!"; fos.write(data.getBytes()); // Flush the output stream to ensure data is written to file fos.flush(); fos.close(); System.out.println("Data written and flushed to file."); } catch (IOException e) { e.printStackTrace(); } } } 

Output

Let us compile and run the above program, this will produce the following result −

 Data written and flushed to file. 

Explanation

• write() writes the data to an internal buffer.

• flush() forces any buffered bytes to be written to the file "example1.txt".

• Without flush(), if the stream wasn't closed properly, some data might remain in the buffer and not reach the file.

Example - Writing a byte array to a file using FileOutputStream

The following example shows the usage of OutputStream write(byte[] b) method.

OutputStreamDemo.java

 package com.tutorialspoint; import java.io.FileOutputStream; import java.io.IOException; public class OutputStreamDemo { public static void main(String[] args) { try { FileOutputStream fos = new FileOutputStream("output1.txt"); String data = "This is an example using write(byte[] b)"; byte[] byteArray = data.getBytes(); // Convert string to byte array fos.write(byteArray); // Write entire byte array to the file fos.close(); System.out.println("Data written to output1.txt"); } catch (IOException e) { e.printStackTrace(); } } } 

Output

Let us compile and run the above program, this will produce the following result −

 Data written to output1.txt 

Explanation

• getBytes() converts a string into a byte array.

• write(byte[] b) writes the entire byte array to the file output1.txt.

• Efficient for writing strings or binary data at once.