how to check if a string does not contain a substring in java code example

Example 1: string contains specific word in java

str_Sample.contains("Example"));

Example 2: string contains specific word in java

public boolean String.contains(CharSequence s);

Example 3: 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");
}