Introduction
Java provides several methods for searching within strings. These methods allow you to check for the presence of a substring, find its position, and more. This tutorial will cover various string searching methods with examples.
Table of Contents
contains()indexOf()lastIndexOf()startsWith()endsWith()matches()- Complete Example Program
- Conclusion
1. contains()
The contains() method checks if a string contains a specified sequence of characters.
Syntax:
public boolean contains(CharSequence s)
Example:
public class ContainsExample {
public static void main(String[] args) {
String str = "Hello, World!";
boolean result = str.contains("World");
System.out.println("Contains 'World': " + result);
}
}
Output:
Contains 'World': true
2. indexOf()
The indexOf() method returns the index within the string of the first occurrence of the specified substring or character. It returns -1 if the substring or character is not found.
Syntax:
public int indexOf(int ch)
public int indexOf(int ch, int fromIndex)
public int indexOf(String str)
public int indexOf(String str, int fromIndex)
Example:
public class IndexOfExample {
public static void main(String[] args) {
String str = "Hello, World!";
int index1 = str.indexOf('o');
int index2 = str.indexOf('o', 5);
int index3 = str.indexOf("World");
int index4 = str.indexOf("world"); // Case-sensitive
System.out.println("Index of 'o': " + index1);
System.out.println("Index of 'o' from index 5: " + index2);
System.out.println("Index of 'World': " + index3);
System.out.println("Index of 'world': " + index4);
}
}
Output:
Index of 'o': 4
Index of 'o' from index 5: 8
Index of 'World': 7
Index of 'world': -1
3. lastIndexOf()
The lastIndexOf() method returns the index within the string of the last occurrence of the specified substring or character. It returns -1 if the substring or character is not found.
Syntax:
public int lastIndexOf(int ch)
public int lastIndexOf(int ch, int fromIndex)
public int lastIndexOf(String str)
public int lastIndexOf(String str, int fromIndex)
Example:
public class LastIndexOfExample {
public static void main(String[] args) {
String str = "Hello, World!";
int index1 = str.lastIndexOf('o');
int index2 = str.lastIndexOf('o', 5);
int index3 = str.lastIndexOf("World");
int index4 = str.lastIndexOf("world"); // Case-sensitive
System.out.println("Last index of 'o': " + index1);
System.out.println("Last index of 'o' from index 5: " + index2);
System.out.println("Last index of 'World': " + index3);
System.out.println("Last index of 'world': " + index4);
}
}
Output:
Last index of 'o': 8
Last index of 'o' from index 5: 4
Last index of 'World': 7
Last index of 'world': -1
4. startsWith()
The startsWith() method checks if a string starts with the specified prefix.
Syntax:
public boolean startsWith(String prefix)
public boolean startsWith(String prefix, int toffset)
Example:
public class StartsWithExample {
public static void main(String[] args) {
String str = "Hello, World!";
boolean result1 = str.startsWith("Hello");
boolean result2 = str.startsWith("World", 7);
System.out.println("Starts with 'Hello': " + result1);
System.out.println("Starts with 'World' from index 7: " + result2);
}
}
Output:
Starts with 'Hello': true
Starts with 'World' from index 7: true
5. endsWith()
The endsWith() method checks if a string ends with the specified suffix.
Syntax:
public boolean endsWith(String suffix)
Example:
public class EndsWithExample {
public static void main(String[] args) {
String str = "Hello, World!";
boolean result = str.endsWith("World!");
System.out.println("Ends with 'World!': " + result);
}
}
Output:
Ends with 'World!': true
6. matches()
The matches() method tells whether this string matches the given regular expression.
Syntax:
public boolean matches(String regex)
Example:
public class MatchesExample {
public static void main(String[] args) {
String str1 = "Hello123";
String str2 = "Hello";
boolean result1 = str1.matches("[A-Za-z0-9]+");
boolean result2 = str2.matches("[A-Za-z0-9]+");
System.out.println("str1 matches regex: " + result1);
System.out.println("str2 matches regex: " + result2);
}
}
Output:
str1 matches regex: true
str2 matches regex: true
7. Complete Example Program
Here is a complete program that demonstrates the various string searching methods discussed above.
Example Code:
public class StringSearchingMethods {
public static void main(String[] args) {
String str = "Hello, World!";
// contains() method
System.out.println("Contains 'World': " + str.contains("World")); // true
// indexOf() method
System.out.println("Index of 'o': " + str.indexOf('o')); // 4
System.out.println("Index of 'o' from index 5: " + str.indexOf('o', 5)); // 8
System.out.println("Index of 'World': " + str.indexOf("World")); // 7
System.out.println("Index of 'world': " + str.indexOf("world")); // -1
// lastIndexOf() method
System.out.println("Last index of 'o': " + str.lastIndexOf('o')); // 8
System.out.println("Last index of 'o' from index 5: " + str.lastIndexOf('o', 5)); // 4
System.out.println("Last index of 'World': " + str.lastIndexOf("World")); // 7
System.out.println("Last index of 'world': " + str.lastIndexOf("world")); // -1
// startsWith() method
System.out.println("Starts with 'Hello': " + str.startsWith("Hello")); // true
System.out.println("Starts with 'World' from index 7: " + str.startsWith("World", 7)); // true
// endsWith() method
System.out.println("Ends with 'World!': " + str.endsWith("World!")); // true
// matches() method
String str1 = "Hello123";
String str2 = "Hello";
System.out.println("str1 matches regex [A-Za-z0-9]+: " + str1.matches("[A-Za-z0-9]+")); // true
System.out.println("str2 matches regex [A-Za-z0-9]+: " + str2.matches("[A-Za-z0-9]+")); // true
}
}
Output:
Contains 'World': true
Index of 'o': 4
Index of 'o' from index 5: 8
Index of 'World': 7
Index of 'world': -1
Last index of 'o': 8
Last index of 'o' from index 5: 4
Last index of 'World': 7
Last index of 'world': -1
Starts with 'Hello': true
Starts with 'World' from index 7: true
Ends with 'World!': true
str1 matches regex [A-Za-z0-9]+: true
str2 matches regex [A-Za-z0-9]+: true
8. Conclusion
Java provides several methods to search within strings, each suited for different needs. The contains() method checks for the presence of a substring, while indexOf() and lastIndexOf() methods find the position of a substring or character. The startsWith() and endsWith() methods check for specific prefixes and suffixes. The matches() method allows you to check if a string matches a given regular expression. Understanding these methods will help you manipulate and analyze strings more effectively in Java.
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