The instanceof Operator: Objects always "know" what type they are. : instanceof Operator « Operators « SCJP

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SCJP » Operators » instanceof Operator

2.7.11.The instanceof Operator: Objects always "know" what type they are.

public class MainClass {

  public static void main(String[] argv) {

    System.out.println();

  }



  public static int checkRefType(Object ref) {

    if (ref instanceof String)

      return 1;

    if (ref instanceof Runnable)

      return 3;

    if (ref instanceof long[])

      return 4;

    return 0;

  }



}

2.7.instanceof Operator
	2.7.1.	instanceof operator determines whether or not a given object is an instance of a particular class.
	2.7.2.	The instanceof operator tests the class of an object at runtime.
	2.7.3.	Using instanceof operator in class hierarchy
	2.7.4.	You cannot use a java.lang.Class object reference.
	2.7.5.	You cannot use a String representing the name of the class as the right operand.
	2.7.6.	The right operand of instanceof may be an interface.
	2.7.7.	Using the instanceof operator to test whether a reference refers to an array.
	2.7.8.	This line is not legal: if (x instanceof [])
	2.7.9.	Determine whether an object is an array using the isArray() method of the Class class.
	2.7.10.	If the left argument of the instanceof operator is a null value, the instanceof test simply returns false;
	2.7.11.	The instanceof Operator: Objects always "know" what type they are.
	2.7.12.	instanceof is for object reference variables only
	2.7.13.	instanceof attempts to downcast
	2.7.14.	test whether the null reference is an instance of a class. This will always result in false.
	2.7.15.	instanceof Compiler Error
	2.7.16.	Operands and Results Using instanceof Operator

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