JAVA EXAMPLE PROGRAMS

JAVA EXAMPLE PROGRAMS

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Program: How to store and read objects from a file?


Description:

Sometimes we need to store the objects to the file system, and need to read them whenever required. Below example shows how to store the objects to the file, and how to retrieve them from the file. ObjectInputStream and ObjectOutputStream classes can help us to store and read objects from a file.


Code:
package com.java2novice.files;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
import java.io.Serializable;

public class MyObjectFileStore {

	public void storeObject(Employee emp){
		
		OutputStream ops = null;
		ObjectOutputStream objOps = null;
		try {
			ops = new FileOutputStream("MyEmpFile.txt");
			objOps = new ObjectOutputStream(ops);
			objOps.writeObject(emp);
			objOps.flush();
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		} finally{
			try{
				if(objOps != null) objOps.close();
			} catch (Exception ex){
				
			}
		}
		
	}
	
	public void displayObjects(){
		
		InputStream fileIs = null;
		ObjectInputStream objIs = null;
		try {
			fileIs = new FileInputStream("MyEmpFile.txt");
			objIs = new ObjectInputStream(fileIs);
			Employee emp = (Employee) objIs.readObject();
			System.out.println(emp);
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} finally {
			try {
				if(objIs != null) objIs.close();
			} catch (Exception ex){
				
			}
		}
		
	}
	
	public static void main(String a[]){
		MyObjectFileStore mof = new MyObjectFileStore();
		Employee e1 = new Employee("Tony",1,"1000");
		mof.storeObject(e1);
		mof.displayObjects();
	}
}

class Employee implements Serializable{
	
	private String name;
	private int id;
	private String salary;
	
	public Employee(String name, int id, String salary){
		this.name = name;
		this.id = id;
		this.salary = salary;
	}
	
	public String toString(){
		return name +"=="+id+"=="+salary;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getSalary() {
		return salary;
	}

	public void setSalary(String salary) {
		this.salary = salary;
	}
}
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Java File IO Operations Sample Code Examples

  1. All file operations.
  2. Show list of all file names from a folder.
  3. How to get list of all files from a folder?
  4. Filter the files by file extensions and show the file names.
  5. How to read file content using byte array?
  6. How to read file content line by line in java?
  7. How to read property file in static context?
  8. How to read input from console in java?
  9. How to get file list from a folder filtered by extensions?
  10. How to get file URI reference?
  11. How to store and read objects from a file?
  12. How to create and store property file dynamically?
  13. How to store property file as xml file?
  14. How to get file last modified time?
  15. How to convert byte array to inputstream?
  16. How to convert inputstream to reader or BufferedReader?
  17. How to convert byte array to reader or BufferedReader?
  18. How to set file permissions in java?
  19. How to read a file using BufferedInputStream?
  20. How to create temporary file in java?
  21. How to write or store data into temporary file in java?
  22. How to delete temporary file in java?
  23. How to write string content to a file in java?
  24. How to write byte content to a file in java?
Knowledge Centre
What is abstract class or abstract method?
We cannot create instance for an abstract class. We can able to create instance for its subclass only. By specifying abstract keyword just before class, we can make a class as abstract class.

public abstract class MyAbstractClass{

}

Abstract class may or may not contains abstract methods. Abstract method is just method signature, it does not containes any implementation. Its subclass must provide implementation for abstract methods. Abstract methods are looks like as given below:

public abstract int getLength();
Famous Quotations
I respect faith, but doubt is what gets you an education.
-- Wilson Mizner

About Author

I'm Nataraja Gootooru, programmer by profession and passionate about technologies. All examples given here are as simple as possible to help beginners. The source code is compiled and tested in my dev environment.

If you come across any mistakes or bugs, please email me to [email protected] or you can comment on the page.

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Reference: Java™ Platform Standard Ed. 7 - API Specification | Java is registered trademark of Oracle.
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