how to check substring is present in string in java code example

Example 1: how to check if a string contains a character

public static boolean containsIgnoreCase(String str, char c) {
        str = str.toLowerCase();

        for (int i = 0; i < str.length(); i++) {
            if (str.charAt(i) == Character.toLowerCase(c)) {
                return true;
            }
        }
        
        return false;
    }

Example 2: string check if substring exists java

String str1 = "Java";
String str2 = "va";

if(str1.contains(str2)){
  // str1.contains(str2) will be true here.
  System.out.println("I am true");
}