Java String Methods

Within the Java programming language, the String class serves as a container for characters arranged in a sequence. This class is a crucial component utilized widely for the storage and manipulation of textual information. It offers a variety of predefined methods that enable developers to perform operations on strings such as extracting substrings, concatenating text segments, altering formatting, comparing texts for equality, and substituting one term with another.

Java String Class Methods

The class java.lang.String offers a variety of helpful functions for manipulating sequences of character values.

Java String Methods Example

Java String.toUpperCase and String.toLowerCase Method

The method String.toUpperCase transforms the text to uppercase, while String.toLowerCase changes it to lowercase.

Example

public class Main {

	public static void main(String ar[]) {

		String s = "Computer";

		System.out.println(s.toUpperCase());

		System.out.println(s.toLowerCase());

		System.out.println(s);

	}

}

Output:

COMPUTER

computer

Computer

Java String.trim Method

This method removes any leading and trailing white spaces from the String.

Example

public class Main {

	public static void main(String ar[]) {

		String s = "  computer ";

		System.out.println(s);

		System.out.println(s.trim());

	}

}

Output:

computer 

computer

Java String.startsWith and String.endsWith Method

The method String.startsWith validates if the initial characters of a String match the specified input, while String.endsWith confirms if the final characters of a String correspond with the provided criteria.

Example

public class Main {

	public static void main(String ar[]) {

		String s = "Computer";

		System.out.println(s.startsWith("C"));// true

		System.out.println(s.endsWith("r"));// true

	}

}

Output:

true

true

Java String.charAt Method

The method String.charAt retrieves and returns the character located at a specific index within a string.

Example

public class Main {

	public static void main(String ar[]) {

		String s = "Laptop";

		System.out.println(s.charAt(2));// S

		System.out.println(s.charAt(1));// h

	}

}

Output:

Java String.length Method

The method String.length provides the length of a specified String.

Example

public class Main {

	public static void main(String ar[]) {

		String s = "Lamborghini";

		System.out.println(s.length());

	}

}

Output:

Java String.intern Method

The class String privately manages a collection of strings, which starts empty.

Upon calling the intern method, if the pool includes a String that matches the current String object based on the equals(Object) method, the String from the pool will be returned. If there is no matching String in the pool, the current String object will be added to the pool, and a reference to it will be returned.

Example

public class Main {

	public static void main(String ar[]) {

		String s = new String("Apple");

		String s2 = s.intern();

		System.out.println(s2);

	}

}

Output:

Java String.valueOf Method

The String.valueOf function converts various data types like integer, long, floating-point, double, boolean, character, and character array into a string representation.

Example

public class Main {

	public static void main(String ar[]) {

		int a = 10;

		String s = String.valueOf(a);

		System.out.println(s + 10);

	}

}

Output:

Java String.replace Method

The method String.replace is used to substitute all instances of a specific set of characters with another set of characters within a string.

Example

public class Main {

	public static void main(String ar[]) {

		String s1 = "Java is a programming language. Java is a platform. Java is an Island.";

		String replaceString = s1.replace("Java", "Kava");// replaces all occurrences of "Java" to "Kava"

		System.out.println(replaceString);

	}

}

Output:

Kava is a programming language. Kava is a platform. Kava is an Island.

Advantages

• ✅ Built-in and Easy to Use: There is no need to write custom logic to handle common string tasks. Java provides many ready-made methods such as length, substring, toLowerCase and many more.
• ✅ Improve Readability of code: Code becomes cleaner and easier to read and understand.
• ✅ Safe and Reliable: String methods reduce the chances of errors as these are tested and stable.

Disadvantages

• ✅ Immutability Can Waste Memory: A new object is created every time we change a string using methods such as replace while doing many changes this is not suitable. Hence, we can use StringBuilder class for the performance purposes.
• ✅ Can Be Slower in Heavy Operations: String methods are slow as compare to alternative methods such as StringBuilder for tasks such as looping over large text or constantly changing in the string method.
• ✅ Null Pointer Risk: We always have to check for null before using string methods. Using methods on a null string throws NullPointerException.

Conclusion

The String class is beneficial for manipulating text effortlessly by offering a variety of handy functions like length, toLowerCase, replace, and more. These functions aid in simplifying our code, enhancing readability, and optimizing our productivity.

In Java, strings are immutable, indicating that they are unable to be altered once they are created. This characteristic can lead to memory wastage when strings are frequently modified. To optimize performance in scenarios where string modifications are frequent, StringBuilder can be utilized.

It is crucial to verify the absence of a value before employing any string operations to prevent potential errors. In general, the String class stands as a vital and robust component within Java development.