instanceof operator determines whether or not a given object is an instance of a particular class. : instanceof Operator « Operators « SCJP

1. SCJP
2. Operators
3. instanceof Operator

public class MainClass {
  public static void main(String[] argv) {
    String s = "string";
    if (s instanceof String) {
      System.out.println("it is a string");
    }
  }
}

it is a string