Java Strings

Strings in Java are objects that can hold a sequence of characters contained within a pair of double quotes (""). Strings are immutable, meaning once a string is created, it cannot be changed. This provides benefits such as better performance, security, and thread safety.

Creating Strings

In Java, there are two ways to create a string:

• Using string literals
• Using the new keyword

Creating Strings Using String Literals

This example uses string literals (“…”) to create a string in Java:

class Main {
  public static void main(String[] args) {
    String s1 = "Hello";

    System.out.println(s1);
  }
}

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Here is the output:

Hello

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Creating Strings Using new

This example uses the new keyword to create a string in Java:

class Main {
  public static void main(String[] args) {
    String s1 = new String("Hello");

    System.out.println(s1);
  }
}

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Here is the output:

Hello

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Accessing String Characters

In Java, an index refers to the numerical position of an element within a data structure like an array or a string.

The charAt() method is used to access string characters.

Here is an example that uses this method to access the first character (index 0) of a Java string:

class Main {
  public static void main(String[] args) {
    String str = "Java";

    // Indexing starts at '0'
    char ch = str.charAt(0);

    System.out.println(ch);
  }
}

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Here is the output:

J

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Get the Length of a String

The length() method can be used to get the length or the number of characters in a string:

String str = "Java Programming";

int len = str.length();

System.out.println("Length: " + len);

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Here is the output:

Length: 16

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Join Two Strings

The concat() method is used to join two strings in Java:

class Main {
  public static void main(String[] args) {
    String first = "Hello ";
    String second = "World";

    String result = first.concat(second);

    System.out.println(result);
  }
}

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Here is the output:

Hello World

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Frequently Asked Questions

1. Are strings in Java mutable?

No, strings in Java are immutable. To create mutable strings, use StringBuilder or StringBuffer.

2. What is the difference between String, StringBuilder, and StringBuffer in Java?

• String is immutable.
• StringBuilder is mutable and not thread-safe.
• StringBuffer is mutable and thread-safe.

3. Can we override methods of the String class in Java?

No. the String class in Java is final, which means it cannot be subclassed.