how to check if a sting contains a substring java code example

Example 1: check if a string contains a character java

string.indexOf('a')

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");
}