Interview Questions on Java - File Handlings

1. How to read a File?

By using FileReader ex:-
FileReader in = new FileReader("file1.txt);;// reads all elemetnts of file1.txt into the Array x.

2. How to write Contents into a file.

By using FileWriter
FileWriter out = new FileWriter("file1.txt");
catch(FileNotFoundException ex)
//some code

3. Can we write the elements line by line by using FileWriter?

No.But you can use BufferedWriter.In BufferedReader you can insert a new line by using newLine();
ex:- out.newLine();

4. Can we read the elements line by line by using FileReader?

No.But you can use BufferedReader.In BufferedReader you can read entire line by using readLine();
ex:- in.readLine();

5. What is Serialization?

Serialization is the process of converting an object into a stream of bytes.

6. What is marker Interface?

Interface which has no methods.

7. What is serializable ?

It is a marker Interface which is used to achieve srialization. Without implementing serializable marker interface we can not do serialization.

8. What is de-serialization?

De-serialization is the process of constructing an object from a stream of bytes.

9. How many ways can we create the objects?

1. By using new() operator.
2. By calling newInstance() method
ex: Class c1 = class.forName(classname);
Object o1 = c1.newInstance();
3. By using Clone() method.
4. while de-serialization
FileInputStream fis = new FileInputStream(file1);
Object o1= in.readObject();

10. What is Externelization?

It is an Interface that extends serializable marker Interface.It is used for attribute wise operation.

11. What is transient variable ?

transient is a key word used for variables to avoid serialization.