Java Youth

Java Tutorial #4

Operator and expressions

Arithmetic operator (+,-,*,/,%)
These can operate on any build in numeric data-type of java except on boolean type ('true' , 'false') . All the arithmetic operators work in the same way as they use to do in C or C++

Modulo operator
Modulo operator mainly gives the remainder of two numbers division.
         Always keep in mind that sign of the result in modulo arithmetic is always the sign of first operand (or dividend)
e.g=> -14%3=-2
           -14%-3=-2
            14%-3=2

Unlike C,C++ modulo operator % can be applied to the floating point data as well
The floating point modulus operator returns the floating point equivalent of an integer division.
                 It simply means that ,the division is carried out with both the floating point operand, but the resulting divisor is treated as integer & resulting in floating remainder will acts as the output of the modulo division of floting point numbers

When arithmetic operation is performed on two different types of data values,the resultant will always be converted into higher precision value

Logical operator

&&
Logical and
can be true only when both the values across && operator should be true

||
Logical or
can be true only when atleast any one the values across || operator should be true

!
Logical not
false if expression is anything other than 0

Special operators

Instanceof opertaor
It is an object reference operator and returns "true" if the object on LHS is an instance of the class on the RHS
This opertor mainly help us to determine whether an object belongs to a particular class or not
          e.g=> person instanceof student
                     will be true if person belongs to the class of student otherwise it will return false

Dot operator
is mainly used to access the instance variable & method of class objects

 e.g=>person.age ;                    //refernce to variable age
      person.salary();                //refrence to the method salary

Remember java doesnot have any operator for exponentiaion (or power), in place it have a method function in math class called pow(a,b) that will implement the same work as being done by the operator, if it would have been.(i.e=>a^b or, a to the power b);

y=(int)(a+b)
here the result is being converted into int value

y=(int)a+b
here a is convered into int value & then being added with b , so the resultant may not be an int value.

Generic typecasting
Typecasting is an unsafe operation because the compiler cannot check the wrong typcast. The compiler throws an exception if typecast fails at runtime
When using generics, the compiler insert typecast at appropriate places to implement type casting. So typecast become implicit in palce of explicit. Generics also detremine the typecast error at compile time rather than runtime
syntax

            Class SampleGenerics
            {
             sample code;
            }
            

e.g=>Illustration of use of generic type in collections
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Following example illustrate how we can print array of different type using a single Generic method:

public class GenericMethodTest
{
   // generic method printArray                         
   public static < E > void printArray( E[] inputArray )
   {
      // Display array elements              
         for ( E element : inputArray ){        
            System.out.printf( "%s ", element );
         }
         System.out.println();
    }

    public static void main( String args[] )
    {
        // Create arrays of Integer, Double and Character
        Integer[] intArray = { 1, 2, 3, 4, 5 };
        Double[] doubleArray = { 1.1, 2.2, 3.3, 4.4 };
        Character[] charArray = { 'H', 'E', 'L', 'L', 'O' };

        System.out.println( "Array integerArray contains:" );
        printArray( intArray  ); // pass an Integer array

        System.out.println( "\nArray doubleArray contains:" );
        printArray( doubleArray ); // pass a Double array

        System.out.println( "\nArray characterArray contains:" );
        printArray( charArray ); // pass a Character array
    } 
}

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Selected important math function
Math functions are the part of java.lang Package
atan2(x,y) =>returns an angle whose tangent is x/y (i.e=> it is tan-inverse
                                                                                               function)
exp(x)=>returns e raised to x
rint(x)=>returns truncated value of x
abs(a)=>returns absolute value of a
Syntax
Math.function_name();
eg=>Math.sqrt(x);