Write a Java Program to Check if a string contains a substring

In Java, you can check whether a given string contains a substring or not using the contains() method of the String class.

The contains() method returns true if the specified substring is present in the given string, otherwise, it returns false.

Here is a Java program that demonstrates how to use the contains() method to check if a string contains a substring:

public class SubstringExample {
   public static void main(String[] args) {
      String str = "Hello, World!";
      String substr1 = "World";
      String substr2 = "Java";
      boolean result1 = str.contains(substr1);
      boolean result2 = str.contains(substr2);
      System.out.println("Result 1: " + result1);
      System.out.println("Result 2: " + result2);
   }
}

In the above program, we have defined a string str and two substrings substr1 and substr2.

We then use the contains() method to check if str contains substr1 and substr2.

The results are stored in result1 and result2 variables and printed on the console.

If you run the above program, you will get the following output:

Result 1: true
Result 2: false

As you can see, the contains() method returns true for substr1 because it is present in str, and false for substr2 because it is not present in str.

In summary, checking if a string contains a substring is a common task in Java programming, and it can be easily done using the contains() method of the String class.

If you need to check for a substring case-insensitively, you can convert both the string and the substring to lowercase or uppercase using the toLowerCase() or toUpperCase() methods of the String class, and then use the contains() method to perform the check.

Here is an example program that demonstrates case-insensitive substring checking:

public class SubstringExample {
   public static void main(String[] args) {
      String str = "Hello, World!";
      String substr1 = "worlD";
      String substr2 = "Java";
      boolean result1 = str.toLowerCase().contains(substr1.toLowerCase());
      boolean result2 = str.toLowerCase().contains(substr2.toLowerCase());
      System.out.println("Result 1: " + result1);
      System.out.println("Result 2: " + result2);
   }
}

In the above program, we convert both str and substr1 to lowercase using the toLowerCase() method, and then use the contains() method to check if str contains substr1 case-insensitively.

The results are stored in result1 and result2 variables and printed on the console.

If you run the above program, you will get the following output:

Result 1: true
Result 2: false

As you can see, the contains() method performs a case-insensitive substring check and returns true for substr1 because it is present in str case-insensitively, and false for substr2 because it is not present in str.

In conclusion, checking if a string contains a substring is a straightforward task in Java, and it can be done using the contains() method of the String class.

If you need to perform a case-insensitive substring check, you can convert both the string and the substring to lowercase or uppercase using the toLowerCase() or toUpperCase() methods of the String class, and then use the contains() method to perform the check.