23-12-24
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Q)What is meant by defining a variable?
=>Within a single statement if variable delcaration and initialization
happens, it is known as defining a variable.
For eg.    
           int a=10;//defining a variable.

Q)What is the output of the following Java application?
class Output{
    public static void main(String args[]){
        int a;
        System.out.println(a);
    }
}
Ans:- The above application causes compilation error.
      => "a" is a local variable.
      =>A variable created within a method is known as a local variable.
      =>Using a local variable without initializing it, is a syntactical error
      in Java.
Q)What is a comment in a Java application?
=>Textual description written within the source code of the application that
is ignored by the Java compiler is nothing but a comment.

=>There are two types of comments in Java.
          1)implementation comments
	  2)documentation comments (used for API creation)
=>There are two types of implementation comments.
        1)single line comments
	2)multi line comments
=>Single line comment starts with "//" and ends with the physical line.
=>Multi-line comment starts with  "/*" and ends with "*/". We can
write any number of lines of textual description here.
Q)What is a data type?
=>data type is the one that specifies the kind of data that can
be stored in Computer's memory.
=>data type specifies a set of values and a set of operations that
can be performed on those values.
Q)How are data types classified in Java?
  1)Primitive data types(pre-defined/system-defined/fundamental/basic  data types)
  2)User defined data types.

Q)What are the primitive data types in Java?
=>To represent numbers, 6 primitive data types are given in Java. 
      1)byte
      2)short
      3)int
      4)long
      5)float
      6)double
=>To represent integral numbers(without fractioal part)
there are 4 primitive data types.  
           1)byte
	   2)short
	   3)int
	   4)long.
=>To represent decimal data (with fractional part) we have 2 data types
in Java.
  1)float
  2)double
=>To represent character data, "char" data type is given.
=>to represent true/false values  "boolean" data type is given.

Q)What is the output of the following application?
class Output{
    public static void main(String args[]){
       float s=10.5;
	   System.out.println(s);
    }
}

Ans:- The above application cuases compilation error.
Reason:- 10.5 is decimal literal. When a decimal literal is used in the source
code, Java compiler treats it by default as "double data type". But here, "s"
of float type.
=>We can fix it as follows.
    double s=10.5;
        OR
    float s=10.5F;
        OR
    float s=10.5f;