Question

1. Explain the differences between primitive and reference data types.
2. Define the scope of a variable (hint: local and global variable)
3. Why is initialization of variables required.
4. Differentiate between static, instance and local variables.
5. Differentiate between widening and narrowing casting in java.
6. the following table shows data type, its size, default value and the range. Filling in the missing values.

TYPE	SIZE (IN BYTES)	DEFAULT	RANGE
boolean	1 bit		true, false
Char	2		‘\0000’ to ‘\ffff’
Byte		0
Short		0	-215 to +215-1
Int	4
Long		0L	-
Float	4	00.0f
Double	8		-1.8E+308 to +1.8E+308

7. Define package as used in java programming
8. Explain the importance of using Java packages

Answer 1

All the basics data types are available in JAVA are primitive types like int, boolean, char, short, etc.

and Reference types are used to point the object like String, File, Thread, etc.

main difference is that primitive types will always has a value while reference type is "NULL" , if int variabe is unintialized then it will have 0 value but if String variable is uninitialized then it will be "null".

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global variable are declared outside any function can be accessed into any function but local variables are declared within any function canbe accessed only in that function.

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initializing variables are useful for preventing bugs specifically for reference type initialization can be useful for preventing null reference errors.

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static variables are variables declared with static keyword outside of any method within class

instance variables are specific to instance of any class they are declared in class but outside of method and also called member variable

while local variable are only declared within any method and can be accessed by that method.

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in simple term widening mean conversion of value to data type that can handle any possible value of original data type , and also widening conversions preserve the source value but can change its representation like short to int.

narrowing mean conversion to data type that might not be able to handle the value of current data type like from float to int, or int to short.

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TYPE	SIZE (IN BYTES)	DEFAULT	RANGE
boolean	1 bit	false	true, false
Char	2 bytes	\0000	‘\0000’ to ‘\ffff’
Byte	1bytes	0	-128 to 127
Short	2bytes	0	-215 to +215-1
Int	4bytes	0	-2147483648 to 2147483647
Long	8bytes	0L	-9223372036854775808 to 9223372036854775807
Float	4bytes	00.0f	±1.4E-45 to ±3.4028235E+38
Double	8bytes	0.0	-1.8E+308 to +1.8E+308

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package is mechanism to grouping the classes, subpackages, and interfaces.

importance are: they are useful in preventing naming conflict, packages are useful for providing controlled access to classes and interfaces, packages are useful in data-hiding because they are actualy encapsulation of related classes and interfaces .