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| Basic Operations |
Basic Operations
Java supports the following operations on variables:
-
Arithmetic :
Addition (+),Subtraction (-),Multiplication (*),Division (/),Modulus (%),Increment (++),Decrement (--). -
String concatenation:
+can be used for String concatenation, but subtraction-on a String is not a valid operation. In java + operator is overloaded on functionality to concatenate strings and to perform addition information -
Relational:
Equal to (==),Not Equal to (!=),Greater than (>),Less than (<),Greater than or equal to (>=),Less than or equal to (<=)Always remember sign of greater and less than always come before assign i.e "=" -
Bitwise:
Bitwise And (&),Bitwise Or (|),Bitwise XOR (^),Bitwise Compliment (~),Left shift (<<),Right Shift (>>),Zero fill right shift (>>>). **Bitwise operators are used to perform bitwise operation in places where calculation on binary numbers are required like-in ciphers,and to design virtual electronic circut replication etc. ** -
Logical:
Logical And (&&),Logical Or (||),Logical Not (!) -
Assignment:
=,+=,-=,*=,/=,%=,<<=,>>=,&=,^=,|= -
Others:
Conditional/Ternary(?:),instanceof**Ternary because it work on the functionality of If Then Else i.e If condition is right then first alternative anotherwise the second one ** While most of the operations are self-explanatory, the Conditional (Ternary) Operator works as follows:
expression that results in boolean output ? return this value if true : return this value if false;
The Assignment operators (+=, -=, *=, /=, %=, <<=, >>=, &=, ^=, |=) are just a short form which can be extended.
Example:
(a += b) does the same thing as (a = a + b)!
Example: True Condition:
int x = 10;
int y = (x == 10) ? 5 : 9; // y will equal 5 since the expression x == 10 evaluates to true
False Condition:
int x = 25;
int y = (x == 10) ? 5 : 9; // y will equal 9 since the expression x == 10 evaluates to false
The instanceof operator is used for type checking. It can be used to test if an object is an instance of a class, a subclass or an interface. General format-
object instance of class/subclass/interface
Here is a program to illustrate the instanceof operator:
Person obj1 = new Person();
Person obj2 = new Boy();
// As obj is of type person, it is not an
// instance of Boy or interface
System.out.println("obj1 instanceof Person: " + (obj1 instanceof Person)); /*it returns true since obj1 is an instance of person */
Operation of ASSIGNMENT Operators explained:
Often times students come across questions in exam/quizes involving complex equations/relations between different variables established with different combinations of assignmen operators. On face, they look preety ambiguous. But follwoing a simpe rule might make solving them preety straigh forward. The rule itself is simple... On any circumstance, first one must deal with PRE-operations, then 'Assignment' operator and then finally comes with 'POST - operations'.
In summary, the order of operation is -
Step 1. PRE-operations
Step 2. Assignment
Step 3. POST - operations.
For example:
int a = 1;
int b;
int b = a-- + ++a ;
What will be the value of a & b after the program compiles?
Step 1. PRE-operations:
a is assigned value 1.
Upon pre-assignment, it becomes 2(since it is '+' here)
Step 2. Assignment:
At this point,
a = 2
and for b ,
b =a-- + ++a
or, b = 2-- + 2 = 4. [Note:POST - operations has not yet come to play yet]
Step 3. POST - operations:
At this point, b = 4 a = 2. But WAIT, there's still one 'post operation' on a to deal with... i.e. a--
So it follows:
a-- // 2-- = 1 (since it is '-' here).
Again, consider this example:
int num1 = 10;
int num2 = 0;
int num3 = 4;
int num4 = 6;
num3 = ++num1 - num4++;
What will be the value of num3 & num4 ?
num3 = 5
num4 = 7