How do you know a variable type in java?

Question

Let\'s say I declare a variable:

String a = \"test\";

And I want to know what type it is, i.e., the output should be java.lang.String

Answer 1

I think we have multiple solutions here:

• instance of could be a solution.

Why? In Java every class is inherited from the Object class itself. So if you have a variable and you would like to know its type. You can use

• System.out.println(((Object)f).getClass().getName());

or

• Integer.class.isInstance(1985); // gives true

or

• isPrimitive()

  public static void main(String[] args) {
  
   ClassDemo classOne = new ClassDemo();
   Class classOneClass = classOne();
  
   int i = 5;
   Class iClass = int.class;
  
   // checking for primitive type
   boolean retval1 = classOneClass.isPrimitive();
   System.out.println("classOneClass is primitive type? = " + retval1);
  
   // checking for primitive type?
   boolean retval2 = iClass.isPrimitive();
   System.out.println("iClass is primitive type? = " + retval2);
  }
  

This going to give us:

1. FALSE
2. TRUE

Find out more here: How to determine the primitive type of a primitive variable?

https://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html

http://docs.oracle.com/cd/E26806_01/wlp.1034/e14255/com/bea/p13n/expression/operator/Instanceof.html