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Java String Methods : How To Create And Methods Of Java String

Java language has many methods for manipulating strings. The sooner you understand these methods, the more effectively you can handle strings in your Java applications. It provides a multitude of methods through which to perform operations on strings. Understanding these methods is the key to effective string handling. This article explains a variety of methods in Java String Methods and shows examples of those methods.

What is a String in Java?

A string is a sequence of characters that shows text. The class String belongs to the package “Java.lang” and is one of the most common types of data used to handle text in Java programs. This class contains many methods through which text may be manipulated and interrogated; hence, it provides the textual data process efficiency.

Using  char[] array in Java

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Using String class in Java

The following program demonstrates the use of String in Java: 

Output

How to Create a String Object?

There are two ways to make the String Object:

• Using String Literal
• Using new keyword

String Literal and String Constant Pool 

In computer science, a literal is a notation representing a value. A Java string literal can be created and represented using double quotes. All of the content/characters can be added between the double quotes.

The following program demonstrates the String Literal:

Program

Output 

String Constant Pool

The String Constant Pool, also known as the String Intern Pool, is a special memory area in the Java Virtual Machine (JVM). It stores string literals and provides memory efficiency and performance optimization for strings.

Example

String str1 = “Neeraj Kumar”;

String str2 = “String 2 stored  here”;

In the above example, it is the only string object created in the string constant pool when two strings are created using the string literal method.

By New Keyword 

The ‘new’ keyword in Java creates objects dynamically at runtime when you use the ‘new’ operator. This operator allocates memory for a new object or array and returns a reference to that memory location.  Unlike string literals, these objects allocate separate memory space in the heap, regardless of whether the same value already exists in the heap or not.

Syntax

String stringName = new String(“string_value”);

The following program demonstrates the new keyword. 

Program

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Example of Strings in Java 

The following program demonstrates the strings in Java language.

Program

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Methods of Java Strings

●    int length() Method

The length() method of string in Java. It is used to get the string length in the Java program.

Syntax:

stringName.length() 

The following program demonstrates the length() method:

Program         

Output

●    char charAt(int index) Method

The charAt() method retrieves a character from a string at a specific position.It is particularly useful when accessing individual characters within a string for comparison, analysis, or processing.

The following program demonstrates the charAt(int index) Method:

Program

Output

●    String concat(String string1) Method

The ‘concat()’ method joins two strings together. It is a powerful method that connects one string to the end of another, resulting in a new string.

Method Signature

public String concat(String str1)

The following program demonstrates the String concat() Method: 

Program

Output

●    String substring(int beginIndex, int index[optional]) method

The substring() method extracts the string portion from the substring. This method is useful when you are working on the specific parts of a string rather than the entire string.

The following program demonstrates the substring() method in Java:

Program

Output 

●    String.equals(String anotherString) method

The equals() method compares two strings for equality. It returns true if the strings are identical; otherwise, it returns false. If the specified string is ‘null’ , the method will return ‘false’, as a non-null string cannot be equal to ‘null’.

Method Signature

public boolean equals(Object anotherString)

The following program demonstrates the String.equals() method:

Program

Output

●    String contains (String substring) Method

The contains() method in Java checks if a string contains a specified substring. If the string contains the specific string, It will return true. Otherwise, it will return false.

The following program demonstrates the String contains method:

Program

Output

●    String join() method

The ‘join()’ method in Java concatenates the elements of a sequence(like an array or an iterable) into a single string, with each element separated by a specified delimiter. This method was introduced in Java 8.

The following program demonstrates the String join() method:

Program 

Output

●    String toUpperCase() Method

The toUpperCase() method is a string method in Java. It converts the string’s lowercase characters to uppercase (or capital) characters.

The following program demonstrates the toUpperCase() Method:

Program

Output

●    String toLowerCase() Method

The ‘toLowerCase()” method converts all the characters into their lowercase equivalents. It is part of the ‘String’ class and It is very useful for case-insensitive comparison or standardizing text.

The following program demonstrates the “toLowerString()” method:

Program

Output

●    String trim() Method

The string trim() method in Java trims or removes the extra white space from the specified string at both ends.

The following program demonstrates the trim() method:

Program

Output

●    String replace(char oldChar, char newChar)

The replace() method in Java is a string manipulation tool that allows you to replace occurrences of a specific character or sequences of characters in a string with another character or sequence. This method is particularly useful when modifying dynamic strings during runtime.

The following program demonstrates the replace() method:

Progra 

Output

To handle strings and process data efficiently, like string manipulation, we must know Java’s methods. These methods (e.g., charAt(), concat, etc.) allow developers to carry out tasks on strings, such as accessing a character, concatenating multiple strings together, extracting part of the string, or replacing one letter or sequence in another. Some of these techniques are the backbone for many text-based applications. Knowing how they are used can lead to the writing of cleaner and more concise Java source code.