String, String Array and its simple operations

String and String Array

• Strings in Java are Objects.
• String is a simple char array. 
• An Arrays are immutable, Strings are immutable as well. 
• Whenever a change to a String is made, an entirely new String is created.
• Immutable string which means a constant and cannot be changed once created.

Syntax:
String string_variable= “character_array”;
Example:
String str = "Sarthak";

• Interfaces and Classes in Strings in Java:
• CharBuffer: 
• This class implements the CharSequence interface. 
• This class is used to allow character buffers to be used in place of CharSequences. 
• String: 
• String is a sequence of characters. 
• In java, objects of String are immutable which means a constant and cannot be changed once created.

Using String:

• There are two ways to create string in Java:
• Example: String literal

String s = “Sarthak”;

• Example: Using new keyword

String s = new String (“Sarthak”);

Using StringBuffer: 

• StringBuffer is a peer class of String that provides much of the functionality of strings. 
• String represents fixed-length, immutable character sequences while StringBuffer represents growable and writable character sequences.
• Syntax:

StringBuffer string_object = new StringBuffer(Charcters);

• Example:

StringBuffer s = new StringBuffer("Sarthak");

Using StringBuilder

• The StringBuilder in Java represents a mutable sequence of characters. 
• Since the String Class in Java creates and immutable sequence of characters, the StringBuilder class provides an alternate to String Class, as it creates a mutable sequence of characters.
• Syntax:

StringBuilder string_object = new StringBuilder ();

• Example:

StringBuilder str = new StringBuilder();
str.append("Sarthak");

How to create String array?

• Arrays are used to store multiple values in a single variable, instead of declaring separate variables for each value.
• To declare an array, define the variable type with square brackets.
• Example of declaration:

String[] cars;

• Example of Initialization:

String[] cars = {"Volvo", "BMW", "Ford", "Mazda"};

How to access elements?

• You access an array element by referring to the index number.
• Example:

System.out.println(cars[0]);

How to Change an Array Element?

• To change the value of a specific element, refer to the index number.
• Example:

cars[0] = "Opel";
System.out.println(cars[0]);

How to get array length?

• To find out how many elements an array has, use the length property.
• Example:

String[] cars = {"Volvo", "BMW", "Ford", "Mazda"};
System.out.println(cars.length);

How to use Loop Through an Array?

• You can loop through the array elements with the for loop, and use the length property to specify how many times the loop should run.
• Example:

String[] cars = {"Volvo", "BMW", "Ford", "Mazda"};
for (int i = 0; i < cars.length; i++) {
  System.out.println(cars[i]);
}

How to use Loop Through an Array with For-Each?

• There is also a "for-each" loop, which is used exclusively to loop through elements in arrays.
• Example:

String[] cars = {"Volvo", "BMW", "Ford", "Mazda"};
for (String i : cars) {
  System.out.println(i);
}