Groovy: Assignment vs if statement

An assignment statement is not allowed as a top-level expression in if statement.

For example,

HelloWorld.groovy

if(a = 10){
 println "a is evaluated to true"
}else{
 println "a is evaluated to false"
}

As you see above snippet, you may think if statement evaluates to true (Since non-zero numbers are considered as true in groovy), but Groovy do not allow top level assignment statements.

You can perform the trick like by embedding the expression in extra parenthesis.

HelloWorld.groovy

if((a = 10)){
 println "a is evaluated to true"
}else{
 println "a is evaluated to false"
}

Output

a is evaluated to true

Previous                                                 Next                                                 Home

Other Operators in Java

Assignment Operator

   Assignment operator is used to assign a value to a variable.

   Syntax

      type variable = value;

   Example

      int a = 10.

      int b = 20

Java supports compound assignments

   Compound Assignment

      Syntax:

         variable operator= value

      Example:

         lets say

         int a = 10;

         a+=10 evaluates to a=a+10

Compound Operator	Example	Description
+=	a+=10	a=a+10
-=	a-=10	a=a-10
*=	a*=10	a=a*10
/=	a/=10	a=a/10

Example Program

class CompoundAssignment{
 public static void main(String args[]){
  int var1 = 100;
  int sum=10, sub=10, mul=10, div=1000;

  System.out.println("sum+var1 is " + (sum+=var1));
  System.out.println("sub-var1 is " + (sub-=var1));
  System.out.println("mul*var1 is " + (mul*=var1));
  System.out.println("div/var1 is" + (div/=var1));
 }
}

         

Output

sum+var1 is 110
sub-var1 is -90 
mul*var1 is 1000 
div/var1 is10

The Type Comparison Operator instanceof

The instanceof operator compares an object to a specified type. You can use it to test if an object is an instance of a class, an instance of a subclass, or an instance of a class that implements a particular interface.

Example

class InstanceOfEx{
 public static void main(String args[]){
  Object obj = new Object();
  System.out.println(obj instanceof Object);
  System.out.println(obj instanceof InstanceOfEx);
 }
}

Output

true
false

   

Don't worry much about this program, you will learn about this while discussing about class and object.

Ternary operator( ?: )

   Returns one of two expressions depending on a condition.

    Syntax

       test ? expression1 : expression2

          Returns expression1 if the “test” condition evaluates to true other wise returns expression 2.

Example

class TernaryEx{
 public static void main(String args[]){
  int a = 100;
  
  int flag = a>10 ? 1 : 0;
  System.out.println(flag);
  
  flag = a>1000 ? 1 : 0;
  System.out.println(flag);
 }
}

Output

1
0

Observation

See the statement “flag = a>10 ? 1 : 0”, a>10 is true, so 1 is returned and assigned to the flag

Bit wise operators                                                 Control flow statements                                                 Home