☕Java Programming

Java String Methods

Updated 2026-05-12

30 min read

Java String Methods

In the world of programming, strings are fundamental data types used extensively for storing and manipulating text. In Java, the String class provides a rich set of methods to perform various operations on string data. Understanding these methods is crucial for any developer working with Java, as they allow you to manipulate text efficiently and effectively.

In this tutorial, we will explore the most commonly used String methods in Java, providing examples and explanations for each. Whether you're a beginner or an experienced developer, this guide will equip you with the knowledge needed to handle strings more proficiently.

Core Content

1. Basic Methods

1.1 length()

The length() method returns the number of characters in a string.

LengthExample.java

1public class LengthExample {
2  public static void main(String[] args) {
3      String str = "Hello, World!";
4      int length = str.length();
5      System.out.println("Length of the string: " + length);
6  };
7}

Output

Length of the string: 13

1.2 charAt(int index)

The charAt(int index) method returns the character at the specified index in a string.

CharAtExample.java

1public class CharAtExample {
2  public static void main(String[] args) {
3      String str = "Hello, World!";
4      char ch = str.charAt(7);
5      System.out.println("Character at index 7: " + ch);
6  }
7}

Output

Character at index 7: W

2. Concatenation Methods

2.1 concat(String str)

The concat(String str) method concatenates the specified string to the end of this string.

ConcatExample.java

1public class ConcatExample {
2  public static void main(String[] args) {
3      String str1 = "Hello";
4      String str2 = " World!";
5      String result = str1.concat(str2);
6      System.out.println("Concatenated string: " + result);
7  }
8}

Output

Concatenated string: Hello World!

2.2 + Operator

The + operator can also be used to concatenate strings.

PlusOperatorExample.java

1public class PlusOperatorExample {
2  public static void main(String[] args) {
3      String str1 = "Hello";
4      String str2 = " World!";
5      String result = str1 + str2;
6      System.out.println("Concatenated string: " + result);
7  }
8}

Output

Concatenated string: Hello World!

3. Substring Methods

3.1 substring(int beginIndex)

The substring(int beginIndex) method returns a new string that is a substring of this string.

SubstringExample.java

1public class SubstringExample {
2  public static void main(String[] args) {
3      String str = "Hello, World!";
4      String subStr = str.substring(7);
5      System.out.println("Substring from index 7: " + subStr);
6  }
7}

Output

Substring from index 7: World!

3.2 substring(int beginIndex, int endIndex)

The substring(int beginIndex, int endIndex) method returns a new string that is a substring of this string.

SubstringRangeExample.java

1public class SubstringRangeExample {
2  public static void main(String[] args) {
3      String str = "Hello, World!";
4      String subStr = str.substring(0, 5);
5      System.out.println("Substring from index 0 to 5: " + subStr);
6  }
7}

Output

Substring from index 0 to 5: Hello

4. Comparison Methods

4.1 equals(Object anObject)

The equals(Object anObject) method compares this string to the specified object.

EqualsExample.java

1public class EqualsExample {
2  public static void main(String[] args) {
3      String str1 = "Hello";
4      String str2 = "Hello";
5      boolean isEqual = str1.equals(str2);
6      System.out.println("Are the strings equal? " + isEqual);
7  }
8}

Output

Are the strings equal? true

4.2 compareTo(String anotherString)

The compareTo(String anotherString) method compares two strings lexicographically.

CompareToExample.java

1public class CompareToExample {
2  public static void main(String[] args) {
3      String str1 = "Apple";
4      String str2 = "Banana";
5      int result = str1.compareTo(str2);
6      System.out.println("Comparison result: " + result);
7  }
8}

Output

Comparison result: -1

5. Case Conversion Methods

5.1 toUpperCase()

The toUpperCase() method converts all the characters in this string to uppercase.

ToUpperCaseExample.java

1public class ToUpperCaseExample {
2  public static void main(String[] args) {
3      String str = "Hello, World!";
4      String upperCaseStr = str.toUpperCase();
5      System.out.println("Uppercase string: " + upperCaseStr);
6  }
7}

Output

Uppercase string: HELLO, WORLD!

5.2 toLowerCase()

The toLowerCase() method converts all the characters in this string to lowercase.

ToLowerCaseExample.java

1public class ToLowerCaseExample {
2  public static void main(String[] args) {
3      String str = "Hello, World!";
4      String lowerCaseStr = str.toLowerCase();
5      System.out.println("Lowercase string: " + lowerCaseStr);
6  }
7}

Output

Lowercase string: hello, world!

6. Trimming Methods

6.1 trim()

The trim() method removes leading and trailing whitespace from this string.

TrimExample.java

1public class TrimExample {
2  public static void main(String[] args) {
3      String str = "   Hello, World!   ";
4      String trimmedStr = str.trim();
5      System.out.println("Trimmed string: '" + trimmedStr + "'");
6  }
7}

Output

Trimmed string: 'Hello, World!'

7. Replacement Methods

7.1 replace(char oldChar, char newChar)

The replace(char oldChar, char newChar) method returns a new string resulting from replacing all occurrences of oldChar in this string with newChar.

ReplaceExample.java

1public class ReplaceExample {
2  public static void main(String[] args) {
3      String str = "Hello, World!";
4      String replacedStr = str.replace('o', 'a');
5      System.out.println("Replaced string: " + replacedStr);
6  }
7}

Output

Replaced string: Hella, Warld!

7.2 replace(CharSequence target, CharSequence replacement)

The replace(CharSequence target, CharSequence replacement) method returns a new string resulting from replacing all occurrences of the literal target sequence in this string with the specified literal replacement.

ReplaceSequenceExample.java

1public class ReplaceSequenceExample {
2  public static void main(String[] args) {
3      String str = "Hello, World!";
4      String replacedStr = str.replace("World", "Java");
5      System.out.println("Replaced string: " + replacedStr);
6  }
7}

Output

Replaced string: Hello, Java!

8. Splitting Methods

8.1 split(String regex)

The split(String regex) method splits this string around matches of the given regular expression.

SplitExample.java

1public class SplitExample {
2  public static void main(String[] args) {
3      String str = "Hello,World,This,Is,Java";
4      String[] parts = str.split(",");
5      for (String part : parts) {
6          System.out.println(part);
7      }
8  }
9}

Output

Hello
World
This
Is
Java

Practical Example

Let's create a practical example that demonstrates the use of several string methods to process user input.

Java

1import java.util.Scanner;
2 
3public class StringManipulationExample {
4  public static void main(String[] args) {
5      Scanner scanner = new Scanner(System.in);
6      System.out.println("Enter a sentence:");
7      String input = scanner.nextLine();
8 
9      // Length of the string
10      int length = input.length();
11      System.out.println("Length of the input: " + length);
12 
13      // Convert to uppercase and lowercase
14      String upperCaseInput = input.toUpperCase();
15      String lowerCaseInput = input.toLowerCase();
16      System.out.println("Uppercase: " + upperCaseInput);
17      System.out.println("Lowercase: " + lowerCaseInput);
18 
19      // Trim whitespace
20      String trimmedInput = input.trim();
21      System.out.println("Trimmed Input: '" + trimmedInput + "'");
22 
23      // Replace a character
24      String replacedInput = input.replace('a', 'e');
25      System.out.println("Replaced 'a' with 'e': " + replacedInput);
26 
27      // Split the string into words
28      String[] words = input.split("s+");
29      System.out.println("Words in the sentence:");
30      for (String word : words) {
31          System.out.println(word);
32      }
33 
34      scanner.close();
35  }
36}

Summary

Method	Description
`length()`	Returns the length of the string.
`charAt(int index)`	Returns the character at the specified index.
`concat(String str)`	Concatenates the specified string to this string.
`substring(int beginIndex)`	Returns a substring from the specified index.
`equals(Object anObject)`	Compares this string with the specified object.
`compareTo(String anotherString)`	Compares two strings lexicographically.
`toUpperCase()`	Converts all characters to uppercase.
`toLowerCase()`	Converts all characters to lowercase.
`trim()`	Removes leading and trailing whitespace.
`replace(char oldChar, char newChar)`	Replaces occurrences of a character.
`split(String regex)`	Splits the string around matches of a regular expression.

What's Next?

In the next tutorial, we will explore Java Math Methods, which provide various mathematical operations and functions. These methods are essential for performing calculations in your Java programs. Stay tuned!

☕Java Programming

Java String Methods

Updated 2026-05-12

30 min read

Java String Methods

Core Content

1. Basic Methods

1.1 length()

The length() method returns the number of characters in a string.

LengthExample.java

1public class LengthExample {
2  public static void main(String[] args) {
3      String str = "Hello, World!";
4      int length = str.length();
5      System.out.println("Length of the string: " + length);
6  };
7}

Output

Length of the string: 13

1.2 charAt(int index)

The charAt(int index) method returns the character at the specified index in a string.

CharAtExample.java

1public class CharAtExample {
2  public static void main(String[] args) {
3      String str = "Hello, World!";
4      char ch = str.charAt(7);
5      System.out.println("Character at index 7: " + ch);
6  }
7}

Output

Character at index 7: W

2. Concatenation Methods

2.1 concat(String str)

The concat(String str) method concatenates the specified string to the end of this string.

ConcatExample.java

1public class ConcatExample {
2  public static void main(String[] args) {
3      String str1 = "Hello";
4      String str2 = " World!";
5      String result = str1.concat(str2);
6      System.out.println("Concatenated string: " + result);
7  }
8}

Output

Concatenated string: Hello World!

2.2 + Operator

The + operator can also be used to concatenate strings.

PlusOperatorExample.java

1public class PlusOperatorExample {
2  public static void main(String[] args) {
3      String str1 = "Hello";
4      String str2 = " World!";
5      String result = str1 + str2;
6      System.out.println("Concatenated string: " + result);
7  }
8}

Output

Concatenated string: Hello World!

3. Substring Methods

3.1 substring(int beginIndex)

The substring(int beginIndex) method returns a new string that is a substring of this string.

SubstringExample.java

1public class SubstringExample {
2  public static void main(String[] args) {
3      String str = "Hello, World!";
4      String subStr = str.substring(7);
5      System.out.println("Substring from index 7: " + subStr);
6  }
7}

Output

Substring from index 7: World!

3.2 substring(int beginIndex, int endIndex)

The substring(int beginIndex, int endIndex) method returns a new string that is a substring of this string.

SubstringRangeExample.java

1public class SubstringRangeExample {
2  public static void main(String[] args) {
3      String str = "Hello, World!";
4      String subStr = str.substring(0, 5);
5      System.out.println("Substring from index 0 to 5: " + subStr);
6  }
7}

Output

Substring from index 0 to 5: Hello

4. Comparison Methods

4.1 equals(Object anObject)

The equals(Object anObject) method compares this string to the specified object.

EqualsExample.java

1public class EqualsExample {
2  public static void main(String[] args) {
3      String str1 = "Hello";
4      String str2 = "Hello";
5      boolean isEqual = str1.equals(str2);
6      System.out.println("Are the strings equal? " + isEqual);
7  }
8}

Output

Are the strings equal? true

4.2 compareTo(String anotherString)

The compareTo(String anotherString) method compares two strings lexicographically.

CompareToExample.java

1public class CompareToExample {
2  public static void main(String[] args) {
3      String str1 = "Apple";
4      String str2 = "Banana";
5      int result = str1.compareTo(str2);
6      System.out.println("Comparison result: " + result);
7  }
8}

Output

Comparison result: -1

5. Case Conversion Methods

5.1 toUpperCase()

The toUpperCase() method converts all the characters in this string to uppercase.

ToUpperCaseExample.java

1public class ToUpperCaseExample {
2  public static void main(String[] args) {
3      String str = "Hello, World!";
4      String upperCaseStr = str.toUpperCase();
5      System.out.println("Uppercase string: " + upperCaseStr);
6  }
7}

Output

Uppercase string: HELLO, WORLD!

5.2 toLowerCase()

The toLowerCase() method converts all the characters in this string to lowercase.

ToLowerCaseExample.java

1public class ToLowerCaseExample {
2  public static void main(String[] args) {
3      String str = "Hello, World!";
4      String lowerCaseStr = str.toLowerCase();
5      System.out.println("Lowercase string: " + lowerCaseStr);
6  }
7}

Output

Lowercase string: hello, world!

6. Trimming Methods

6.1 trim()

The trim() method removes leading and trailing whitespace from this string.

TrimExample.java

1public class TrimExample {
2  public static void main(String[] args) {
3      String str = "   Hello, World!   ";
4      String trimmedStr = str.trim();
5      System.out.println("Trimmed string: '" + trimmedStr + "'");
6  }
7}

Output

Trimmed string: 'Hello, World!'

7. Replacement Methods

7.1 replace(char oldChar, char newChar)

The replace(char oldChar, char newChar) method returns a new string resulting from replacing all occurrences of oldChar in this string with newChar.

ReplaceExample.java

1public class ReplaceExample {
2  public static void main(String[] args) {
3      String str = "Hello, World!";
4      String replacedStr = str.replace('o', 'a');
5      System.out.println("Replaced string: " + replacedStr);
6  }
7}

Output

Replaced string: Hella, Warld!

7.2 replace(CharSequence target, CharSequence replacement)

ReplaceSequenceExample.java

1public class ReplaceSequenceExample {
2  public static void main(String[] args) {
3      String str = "Hello, World!";
4      String replacedStr = str.replace("World", "Java");
5      System.out.println("Replaced string: " + replacedStr);
6  }
7}

Output

Replaced string: Hello, Java!

8. Splitting Methods

8.1 split(String regex)

The split(String regex) method splits this string around matches of the given regular expression.

SplitExample.java

1public class SplitExample {
2  public static void main(String[] args) {
3      String str = "Hello,World,This,Is,Java";
4      String[] parts = str.split(",");
5      for (String part : parts) {
6          System.out.println(part);
7      }
8  }
9}

Output

Hello
World
This
Is
Java

Practical Example

Let's create a practical example that demonstrates the use of several string methods to process user input.

Java

1import java.util.Scanner;
2 
3public class StringManipulationExample {
4  public static void main(String[] args) {
5      Scanner scanner = new Scanner(System.in);
6      System.out.println("Enter a sentence:");
7      String input = scanner.nextLine();
8 
9      // Length of the string
10      int length = input.length();
11      System.out.println("Length of the input: " + length);
12 
13      // Convert to uppercase and lowercase
14      String upperCaseInput = input.toUpperCase();
15      String lowerCaseInput = input.toLowerCase();
16      System.out.println("Uppercase: " + upperCaseInput);
17      System.out.println("Lowercase: " + lowerCaseInput);
18 
19      // Trim whitespace
20      String trimmedInput = input.trim();
21      System.out.println("Trimmed Input: '" + trimmedInput + "'");
22 
23      // Replace a character
24      String replacedInput = input.replace('a', 'e');
25      System.out.println("Replaced 'a' with 'e': " + replacedInput);
26 
27      // Split the string into words
28      String[] words = input.split("s+");
29      System.out.println("Words in the sentence:");
30      for (String word : words) {
31          System.out.println(word);
32      }
33 
34      scanner.close();
35  }
36}

Summary

Method	Description
`length()`	Returns the length of the string.
`charAt(int index)`	Returns the character at the specified index.
`concat(String str)`	Concatenates the specified string to this string.
`substring(int beginIndex)`	Returns a substring from the specified index.
`equals(Object anObject)`	Compares this string with the specified object.
`compareTo(String anotherString)`	Compares two strings lexicographically.
`toUpperCase()`	Converts all characters to uppercase.
`toLowerCase()`	Converts all characters to lowercase.
`trim()`	Removes leading and trailing whitespace.
`replace(char oldChar, char newChar)`	Replaces occurrences of a character.
`split(String regex)`	Splits the string around matches of a regular expression.