03-Strings.md

Strings

Strings in Java are Objects that are backed internally by a char array. Since arrays are immutable(cannot grow), Strings are immutable as well. Whenever a change to a String is made, an entirely new String is created. You will learn more about arrays in comming sections.

Creating a String

The most basic way of creating a string is

String str = "Hello World";

As with any other objects in Java Strings can also created using 'new' keyword

Example 01

public class StringExample{
    public static void main(String[] args){
        // creating character array
        char[] arr = {'h','e','l','l','o'};
        // creating a String object
        String str = new String(arr);
        System.out.println(str);
    }
}

Output

hello

You will learn about Onjects and 'new' keyword in Objects and Classes section.

Some String Methods

Lenght of String

String str = "Hello World";
int len = str.length();
System.out.println(len);

Output

11

Concatenating two strings

String str1 = "Hello";
String str2 = "World";

String str3 = str1.concat(str2);

System.out.println(str3);
System.out.println(str1 + str2);
System.out.println("Hello".concat(str2));
System.out.println("Hello" + "World");

Output

HelloWorld
HelloWorld
HelloWorld
HelloWorld

To get character at given index

Since a String is internally a character array index starts with 0

String str = "Hello World";
System.out.println(str.charAt(0));
System.out.println(str.cahrtAt(6));

Output

H
W

External Resources

Readings

• Oracle Tutorials
• JavaTPoint

Youtube Videos

• ProgrammingKnowledge
• Alex Lee
• Cave of Programming

More Examples and Practice Questions

• W3Resources Solve Questions 1, 2, 7, 11, 12, 13 and 14

If you are confident enough you can try solving other questions also.