The java.lang.String.contains() method searches the sequence of characters in the given string. It returns true if the sequence of char values is found in this string otherwise returns false.
Implementation of contains() method
public boolean contains(CharSequence sequence)
{
return indexOf(sequence.toString()) > -1;
}
Here conversion of CharSequence to a String takes place and then the indexOf method is called. The method indexOf returns O or a higher number if it finds the String, otherwise -1 is returned. So, after execution, contains() method returns true if the sequence of char values exists, otherwise false.
Syntax of contains() method
public boolean contains(CharSequence sequence);
Parameter
- sequence: This is the sequence of characters to be searched.
Exception
- NullPointerException: If seq is null
Examples of the java.string.contains() method
Example 1: To check whether the charSequence is present or not.
Java
// Java program to demonstrate working// contains() methodclass Gfg { // Driver code public static void main(String args[]) { String s1 = "My name is GFG"; // prints true System.out.println(s1.contains("GFG")); // prints false System.out.println(s1.contains("geeks")); }} |
Output
true false
Example 2: Case-sensitive method to check whether given CharSequence is present or not.
Java
// Java code to demonstrate case// sensitivity of contains() methodclass Gfg1 { // Driver code public static void main(String args[]) { String s1 = "Welcome! to GFG"; // prints false System.out.println(s1.contains("Gfg")); // prints true System.out.println(s1.contains("GFG")); }} |
Output
false true
Points to remember with Java string contains() method
- This method does not work to search for a character.
- This method does not find an index of string if it is not present.
- For the above two functionalities, there is a better function String indexOf
