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Unary Operators Reminder These only need one variable (increment by 1) (decrement by 1) 3. variable += x (same as variable = variable + x) 4. variable - = x (same as variable = variable - x) 5. variable *= x (same as variable = variable * x) 6. variable /= x (same as variable = variable / x) 7. variable %= x (same as variable = variable % x)
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JAVAPractical 05 1. Unary operators2. Using Reals3. Conversions4. Type Casting 5. Scope6. Constants
Unary Operators Unary operators such as -- or ++
involve only one variable
For example in order to increase x by 1 the statement x++ is enough
When two variables are used in a calculation it’s called a binary operation
Unary Operators Reminder These only need one variable
1. ++ (increment by 1)2. -- (decrement by 1)3. variable += x (same as variable = variable + x) 4. variable -= x (same as variable = variable - x)5. variable *= x (same as variable = variable * x)6. variable /= x (same as variable = variable / x)7. variable %= x (same as variable = variable % x)
Two ways of Using Unary Operators
Unary operators can be used in two ways;
1. Postfix2. Prefix
Type Statement Equivalent
Postfixn++ n = n +1n-- n = n – 1
Prefix++n n = n + 1--n n =n -1
Example Although the end result is the
same, there is a difference when using postfix or prefix
Output The outputs are the following;
In n++◦ The value of n (9) is stored in x◦ Then n is increased by 1 ◦ Resulting value stored in n
In ++n◦ First n (9) is increased by one ◦ Then the result is stored in x◦ So we end up with the output above
Using RealsWhen numbers with a fraction must
be stored, real type variables must be used;
1. float 2. Double
These can be used just like regular variables
However, when using float the letter f must be added at the end of the number
Example
Conversions When variables are assigned to
other variables for example num1 = num2, one must keep in mind the following:
1. Both variables are of the same data type, or
2. The two variables are compatible,
3. or4. The destination variable type is
larger than the source type.
Examples
byte num2 =13;
short num1 = num2;
This is correct since num1 is short and so it’s a bigger variable type than byte.
long num2;
int num1 = num2;
This is incorrect since we’re trying to fit long data into an int data type and it cannot be done since it’s smaller.
Converting Variable Types We must look at the hierarchy of
variable types in order to know which variables can be converted
Example double is the biggest, so it cannot be converted to anything else; whilst byte (since it’s the smallest) can be converted to any type (except char). Note that boolean data types cannot be converted to anything since they are not numbers
Hierarchy doublefloatlongint
char shortbyte
Type Casting Types can also be changed by
specifying to which type you want to convert them in brackets. For example:
int x = (int) 9.45;This will change 9.45 to an integer (so it
becomes a 9) and stores it in x.
ScopeWhenever the curly brackets are
opened and closed, a scope is created
If a variable is declared in the main scope it can be used throughout the method, however if it is declared between the curly brackets further in the program it will be only available in that scope.
Example
As you can see in the previous example x can be used throughout the program however j can only be used in that scope
Constants A constant is very similar to a variable
The difference is that its values cannot be changed
Hence a constant is read-only
A constant is declared the same as a variable however the keyword final must be used in order to show that it’s a constant
Example For example the mathematical value for PI
never changes,
Hence it can be declared as a constant in our program
In order to identify variables from constants, constants are created using capital letters.
final double PI = 3.142;