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Java – Modifier Types and Basic Operators  December 8, 2016

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Euclid algorithm  December 8, 2016

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Java – Modifier Types and Basic Operators
Modifiers are keywords that you add to those definitions to change their meanings. Java language has a wide variety of modifiers, including the following −
 Java Access Modifiers
 Non Access Modifiers
To use a modifier, you include its keyword in the definition of a class, method, or variable. The modifier precedes the rest of the statement, as in the following example.
Example
public class className { // ... } private boolean myFlag; static final double weeks = 9.5; protected static final int BOXWIDTH = 42; public static void main(String[] arguments) { // body of method }
Access Control Modifiers
Java provides a number of access modifiers to set access levels for classes, variables, methods and constructors. The four access levels are −
 Visible to the package, the default. No modifiers are needed.
 Visible to the class only (private).
 Visible to the world (public).
 Visible to the package and all subclasses (protected).
NonAccess Modifiers
Java provides a number of nonaccess modifiers to achieve many other functionality.
 The static modifier for creating class methods and variables.
 The final modifier for finalizing the implementations of classes, methods, and variables.
 The abstract modifier for creating abstract classes and methods.
 The synchronized and volatile modifiers, which are used for threads.
Java provides a rich set of operators to manipulate variables. We can divide all the Java operators into the following groups −
 Arithmetic Operators
 Relational Operators
 Bitwise Operators
 Logical Operators
 Assignment Operators
 Misc Operators
The Arithmetic Operators
Arithmetic operators are used in mathematical expressions in the same way that they are used in algebra. The following table lists the arithmetic operators −
Assume integer variable A holds 10 and variable B holds 20, then −
Show Examples
Operator  Description  Example 

+ (Addition)  Adds values on either side of the operator.  A + B will give 30 
– (Subtraction)  Subtracts righthand operand from lefthand operand.  A – B will give 10 
* (Multiplication)  Multiplies values on either side of the operator.  A * B will give 200 
/ (Division)  Divides lefthand operand by righthand operand.  B / A will give 2 
% (Modulus)  Divides lefthand operand by righthand operand and returns remainder.  B % A will give 0 
++ (Increment)  Increases the value of operand by 1.  B++ gives 21 
— (Decrement)  Decreases the value of operand by 1.  B– gives 19 
The Relational Operators
There are following relational operators supported by Java language.
Assume variable A holds 10 and variable B holds 20, then −
Show Examples
Operator  Description  Example 

== (equal to)  Checks if the values of two operands are equal or not, if yes then condition becomes true.  (A == B) is not true. 
!= (not equal to)  Checks if the values of two operands are equal or not, if values are not equal then condition becomes true.  (A != B) is true. 
> (greater than)  Checks if the value of left operand is greater than the value of right operand, if yes then condition becomes true.  (A > B) is not true. 
< (less than)  Checks if the value of left operand is less than the value of right operand, if yes then condition becomes true.  (A < B) is true. 
>= (greater than or equal to)  Checks if the value of left operand is greater than or equal to the value of right operand, if yes then condition becomes true.  (A >= B) is not true. 
<= (less than or equal to)  Checks if the value of left operand is less than or equal to the value of right operand, if yes then condition becomes true.  (A <= B) is true. 
The Bitwise Operators
Java defines several bitwise operators, which can be applied to the integer types, long, int, short, char, and byte.
Bitwise operator works on bits and performs bitbybit operation. Assume if a = 60 and b = 13; now in binary format they will be as follows −
a = 0011 1100
b = 0000 1101
—————–
a&b = 0000 1100
ab = 0011 1101
a^b = 0011 0001
~a = 1100 0011
The following table lists the bitwise operators −
Assume integer variable A holds 60 and variable B holds 13 then −
Show Examples
Operator  Description  Example 

& (bitwise and)  Binary AND Operator copies a bit to the result if it exists in both operands.  (A & B) will give 12 which is 0000 1100 
 (bitwise or)  Binary OR Operator copies a bit if it exists in either operand.  (A  B) will give 61 which is 0011 1101 
^ (bitwise XOR)  Binary XOR Operator copies the bit if it is set in one operand but not both.  (A ^ B) will give 49 which is 0011 0001 
~ (bitwise compliment)  Binary Ones Complement Operator is unary and has the effect of ‘flipping’ bits.  (~A ) will give 61 which is 1100 0011 in 2’s complement form due to a signed binary number. 
<< (left shift)  Binary Left Shift Operator. The left operands value is moved left by the number of bits specified by the right operand.  A << 2 will give 240 which is 1111 0000 
>> (right shift)  Binary Right Shift Operator. The left operands value is moved right by the number of bits specified by the right operand.  A >> 2 will give 15 which is 1111 
>>> (zero fill right shift)  Shift right zero fill operator. The left operands value is moved right by the number of bits specified by the right operand and shifted values are filled up with zeros.  A >>>2 will give 15 which is 0000 1111 
The Logical Operators
The following table lists the logical operators −
Assume Boolean variables A holds true and variable B holds false, then −
Show Examples
Operator  Description  Example 

&& (logical and)  Called Logical AND operator. If both the operands are nonzero, then the condition becomes true.  (A && B) is false 
 (logical or)  Called Logical OR Operator. If any of the two operands are nonzero, then the condition becomes true.  (A  B) is true 
! (logical not)  Called Logical NOT Operator. Use to reverses the logical state of its operand. If a condition is true then Logical NOT operator will make false.  !(A && B) is true 
The Assignment Operators
Following are the assignment operators supported by Java language −
Show Examples
Operator  Description  Example 

=  Simple assignment operator. Assigns values from right side operands to left side operand.  C = A + B will assign value of A + B into C 
+=  Add AND assignment operator. It adds right operand to the left operand and assign the result to left operand.  C += A is equivalent to C = C + A 
=  Subtract AND assignment operator. It subtracts right operand from the left operand and assign the result to left operand.  C = A is equivalent to C = C – A 
*=  Multiply AND assignment operator. It multiplies right operand with the left operand and assign the result to left operand.  C *= A is equivalent to C = C * A 
/=  Divide AND assignment operator. It divides left operand with the right operand and assign the result to left operand.  C /= A is equivalent to C = C / A 
%=  Modulus AND assignment operator. It takes modulus using two operands and assign the result to left operand.  C %= A is equivalent to C = C % A 
<<=  Left shift AND assignment operator.  C <<= 2 is same as C = C << 2 
>>=  Bitwise AND assignment operator.  C >>= 2 is same as C = C >> 2 
&=  Right shift AND assignment operator.  C &= 2 is same as C = C & 2 
^=  bitwise exclusive OR and assignment operator.  C ^= 2 is same as C = C ^ 2 
=  bitwise inclusive OR and assignment operator.  C = 2 is same as C = C  2 
Miscellaneous Operators
There are few other operators supported by Java Language.
Conditional Operator ( ? : )
Conditional operator is also known as the ternary operator. This operator consists of three operands and is used to evaluate Boolean expressions. The goal of the operator is to decide, which value should be assigned to the variable. The operator is written as −
variable x = (expression) ? value if true : value if false
Following is an example −
Example
public class Test { public static void main(String args[]) { int a, b; a = 10; b = (a == 1) ? 20: 30; System.out.println( "Value of b is : " + b ); b = (a == 10) ? 20: 30; System.out.println( "Value of b is : " + b ); } }
This will produce the following result −
Output
Value of b is : 30 Value of b is : 20
instanceof Operator
This operator is used only for object reference variables. The operator checks whether the object is of a particular type (class type or interface type). instanceof operator is written as −
( Object reference variable ) instanceof (class/interface type)
If the object referred by the variable on the left side of the operator passes the ISA check for the class/interface type on the right side, then the result will be true. Following is an example −
Example
public class Test { public static void main(String args[]) { String name = "James"; // following will return true since name is type of String boolean result = name instanceof String; System.out.println( result ); } }
This will produce the following result −
Output
true
This operator will still return true, if the object being compared is the assignment compatible with the type on the right. Following is one more example −
Example
class Vehicle {} public class Car extends Vehicle { public static void main(String args[]) { Vehicle a = new Car(); boolean result = a instanceof Car; System.out.println( result ); } }
This will produce the following result −
Output
true
Precedence of Java Operators
Operator precedence determines the grouping of terms in an expression. This affects how an expression is evaluated. Certain operators have higher precedence than others; for example, the multiplication operator has higher precedence than the addition operator −
For example, x = 7 + 3 * 2; here x is assigned 13, not 20 because operator * has higher precedence than +, so it first gets multiplied with 3 * 2 and then adds into 7.
Here, operators with the highest precedence appear at the top of the table, those with the lowest appear at the bottom. Within an expression, higher precedence operators will be evaluated first.
Category  Operator  Associativity 

Postfix  >() [] . (dot operator)  Left toright 
Unary  >++ – – ! ~  Right to left 
Multiplicative  >* /  Left to right 
Additive  >+ –  Left to right 
Shift  >>> >>> <<  Left to right 
Relational  >> >= < <=  Left to right 
Equality  >== !=  Left to right 
Bitwise AND  >&  Left to right 
Bitwise XOR  >^  Left to right 
Bitwise OR  >  Left to right 
Logical AND  >&&  Left to right 
Logical OR  >  Left to right 
Conditional  ?:  Right to left 
Assignment  >= += = *= /= %= >>= <<= &= ^= =  Right to left 
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