The StringBuilder.subSequence()
method in Java is used to extract a subsequence of characters from a StringBuilder
object.
Table of Contents
- Introduction
subSequence
Method Syntax- Examples
- Extracting a Subsequence
- Using a Subsequence in Comparisons
- Real-World Use Case
- Conclusion
Introduction
The StringBuilder.subSequence()
method is a member of the StringBuilder
class in Java. It allows you to extract a specific range of characters as a CharSequence
from the StringBuilder
object. This method is useful when you need a part of the sequence without modifying the original StringBuilder
.
subSequence() Method Syntax
The syntax for the subSequence
method is as follows:
public CharSequence subSequence(int start, int end)
- start: The beginning index, inclusive.
- end: The ending index, exclusive.
The method returns a CharSequence
that starts at the specified start
index and ends at the specified end
index.
Examples
Extracting a Subsequence
The subSequence
method can be used to extract a part of the character sequence from a StringBuilder
.
Example
public class StringBuilderSubSequenceExample {
public static void main(String[] args) {
StringBuilder sb = new StringBuilder("Hello, World!");
// Extract a subsequence from index 7 to 12
CharSequence subSeq = sb.subSequence(7, 12);
// Print the result
System.out.println("Subsequence: " + subSeq);
}
}
Output:
Subsequence: World
Using a Subsequence in Comparisons
You can use the subSequence
method to extract parts of a StringBuilder
for comparisons.
Example
public class StringBuilderSubSequenceExample {
public static void main(String[] args) {
StringBuilder sb1 = new StringBuilder("Hello, World!");
StringBuilder sb2 = new StringBuilder("Hello, Java!");
// Extract subsequences from both StringBuilders
CharSequence subSeq1 = sb1.subSequence(7, 12);
CharSequence subSeq2 = sb2.subSequence(7, 11);
// Compare the subsequences
boolean areEqual = subSeq1.equals(subSeq2);
// Print the result
System.out.println("Subsequence 1: " + subSeq1);
System.out.println("Subsequence 2: " + subSeq2);
System.out.println("Are the subsequences equal? " + areEqual);
}
}
Output:
Subsequence 1: World
Subsequence 2: Java
Are the subsequences equal? false
Real-World Use Case
Example: Extracting a Substring for Validation
In a real-world scenario, you might need to extract and validate parts of a string, such as checking if a certain portion of an input string matches a required format.
Example Code
public class SubstringValidator {
public static void main(String[] args) {
StringBuilder input = new StringBuilder("User12345");
// Extract the numeric part of the string
CharSequence numericPart = input.subSequence(4, input.length());
// Validate if the numeric part contains only digits
boolean isValid = isNumeric(numericPart);
// Print the validation result
System.out.println("Numeric part: " + numericPart);
System.out.println("Is the numeric part valid? " + isValid);
}
public static boolean isNumeric(CharSequence cs) {
for (int i = 0; i < cs.length(); i++) {
if (!Character.isDigit(cs.charAt(i))) {
return false;
}
}
return true;
}
}
Output:
Numeric part: 12345
Is the numeric part valid? true
Conclusion
The StringBuilder.subSequence()
method in Java is used for extracting a subsequence of characters from a StringBuilder
object. By understanding how to use this method, you can efficiently manage and manipulate specific parts of a character sequence. Whether you need to extract a part of the sequence for further processing, perform comparisons, or validate substrings, the subSequence
method provides a reliable solution for these tasks.