Java string lastindexOf Method
What is a string in Java?
In Java, a string object is an object that represents a sequence of characters. A string object is created using the String class, which is a built-in class in Java. Strings are used to represent text data in Java.
- The Java platform provides a rich set of classes and methods for working with strings, making it easy to perform common tasks such as searching, parsing, and formatting strings.
To know more about String Class in java read the complete article.
String lastindexOf() method.
The lastIndexOf() method is a method of the java.lang.String class and is used to find the last occurrence of a specific character or a substring in a given string. It returns the index of the last occurrence of the specified character or substring, or -1 if the character or substring is not found.
- the lastIndexOf() method is case-sensitive, so it will not find a match if the character or substring you are searching for does not match the case of the characters in the string.
Returns
the index of the last occurrence of the character in the character sequence represented by this object that is less than or equal to fromIndex, or -1 if the character does not occur before that point.
Throws:
IndexOutOfBoundsException - if beginIndex is negative or larger than the length of this String object.
Syntax:
public int lastIndexOf(int ch,int fromIndex)
Parameters:
ch - a character (Unicode code point).
Let’s look at a string-related Java program where the Java String LastindexOf() Method is used to perform an operation on the given string.
Example: Java String lastindexOf() Method
public class Main {
public static void main(String[] args) {
String myStr = "PrepInsta Prime has over 200 courses.";
System.out.println(myStr.lastIndexOf("courses"));
}
}
Output
29
Explanation:
The lastIndexOf method is used to find the last occurrence of a specific substring in a string. In this case, it returns the index of the last occurrence of the substring "courses" in the string "PrepInsta Prime has over 200 courses.",
Example 2 : Java String lastindexOf() Method
Run
public class Main {
public static void main(String[] args) {
String myStr = "hello prepinsta.";
System.out.println(myStr.lastIndexOf("h", 5));
}
}
Output
0
Explanation:
This code creates a string called str with the value "Hello World" and then extracts a substring starting at index 6 (the 'W' character) and ending at the end of the string. The substring() method returns a new string containing the characters in the substring, which is then printed to the console using the println() method.
Example 3: how to use the lastindexOf property:
public class Main {
public static void main(String[] args) {
String str = "Hello World";
// Extract a substring starting at index 6 and ending at index 11
String subString = str.substring(6, 11);
// Print the length of the substring
System.out.println("Length: " + subString.length()); // Outputs "Length: 5"
// Check if the substring starts with a specific string
System.out.println("Starts with 'W': " + subString.startsWith("W")); // Outputs "Starts with 'W': true"
// Check if the substring ends with a specific string
System.out.println("Ends with 'd': " + subString.endsWith("d")); // Outputs "Ends with 'd': true"
// Get the character at a specific index in the substring
char c = subString.charAt(2);
System.out.println("Char at index 2: " + c); // Outputs "Char at index 2: r"
// Convert the substring to uppercase
String upperCase = subString.toUpperCase();
System.out.println("Uppercase: " + upperCase); // Outputs "Uppercase: WORLD"
}
}
Output
Length: 5 Starts with 'W': true Ends with 'd': true Char at index 2: r Uppercase: WORLD
Explanation:
This code demonstrates some additional capabilities of the substring() method beyond just extracting a substring from a string. It shows how to get the length of the substring, check if it starts or ends with a specific string, access individual characters within the substring, and convert it to uppercase.
The length() method returns the number of characters in the substring. The startsWith() and endsWith() methods check if the substring starts or ends with a specific string and return true if it does and false if it doesn't. The charAt() method returns the character at a specific index in the substring. The toUpperCase() method returns a new string with all the characters in the substring converted to uppercase.
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