What is a Constructor in Java? In Java, a constructor is a special type of method that is used to initialize objects. When you create an object of a class, the constructor is called automatically. Its main job is to set the initial values of the object’s properties or perform any setup that the object needs before it can be used. Why Do We Need Constructors? You need constructors because: Initialization : Constructors are responsible for initializing an object when it is created. Automatic Execution : A constructor is automatically called when an object is created, so you don’t have to manually initialize every property. Simplifying Object Creation : It simplifies object creation by providing default values or custom initialization. Where Do Constructors Fit in Java? Constructors fit within a class. They are used whenever a new object of that class is created, and they allow the object to be initialized. Constructors must have the same name as the class, and they don't have a re...
File I/O Classes Reading
1. File Class:
- Represents a file or directory path in the file system.
- Provides methods for file manipulation and querying file attributes.
File file = new File("example.txt");
if (file.exists()) {
System.out.println("File exists!");
} else {
System.out.println("File does not exist!");
}
2. FileInputStream:
- Reads raw bytes from a file input stream.
- Suitable for reading binary data from files.
try (FileInputStream fis = new FileInputStream("example.txt")) {
int byteRead;
while ((byteRead = fis.read()) != -1) {
System.out.print((char) byteRead);
}
} catch (IOException e) {
e.printStackTrace();
}
3. BufferedReader:
- Reads text from a character-input stream efficiently by buffering characters.
try (BufferedReader br = new BufferedReader(new FileReader("example.txt"))) {
String line;
while ((line = br.readLine()) != null) {
System.out.println(line);
}
} catch (IOException e) {
e.printStackTrace();
}
4. FileReader:
- Reads character files using the default character encoding.
try (FileReader fr = new FileReader("example.txt")) {
int character;
while ((character = fr.read()) != -1) {
System.out.print((char) character);
}
} catch (IOException e) {
e.printStackTrace();
}
5. Scanner:
- Parses primitive types and strings from the input stream.
- Simplifies the process of reading user input or file contents.
try (Scanner scanner = new Scanner(new File("example.txt"))) {
while (scanner.hasNextLine()) {
System.out.println(scanner.nextLine());
}
} catch (FileNotFoundException e) {
e.printStackTrace();
}
These examples demonstrate how to use various file I/O classes to read data from files in Java.
Comments
Post a Comment