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Cross Ref > Operators

By Mike Prestwood

Java versus C#: A side by side comparison between Java and C#.

 
Operators
 

A language symbol used for assignment, comparison, computational, or as a logical.

Assignment

[Other Languages] 

Languages Focus

Common assignment operators for languages include =, ==, and :=. An assignment operator allows you to assign a value to a variable. The value can be a literal value like "Mike" or 42 or the value stored in another variable or returned by a function.

Java:   =

Java uses = for it's assignment operator.

C#:   =

C# uses = for it's assignment operator.

Syntax Example:
int Age;
string FullName;
  
Age = 42;
FullName = "Randy Spitz";




Comparison Operators

[Other Languages] 

General Info: Round Floating Point Numbers

When comparing floating point numbers, make sure you round to an acceptable level of rounding for the type of application you are using.

Languages Focus

A comparison operator compares two values either literals as in "Hello" and 3 or variables as in X and Counter. Most languages use the same operators for comparing both numbers and strings. Perl, for example, uses separate sets of comparison operators for numbers and strings.

Java:   ==, !=

The Java comparison operators are:

== equal
!= not equal
< less than
> greater than
<= less than or equal
>= greater than or equal

More Info / Comment
C#:   ==, !=

Common comparison operators:

== equal
!= not equal
< less than
> greater than
<= less than or equal
>= greater than or equal

Syntax Example:
//Does C# evaluate the math correctly? No!
if (.1 + .1 + .1 == .3)
MessageBox.Show("correct");
else
MessageBox.Show("not correct");




Empty String Check

[Other Languages] 

Languages Focus

An empty string is a zero length string, a string that is equal to null (""), or not assigned. In some languages, you can check if a string is empty by comparing it to an empty string (""). Some languages distinguish between nil and null ("") so checking if the length is 0 is easier.

Java:   IsEmpty
C#:   String.IsNullOrEmpty

The .Net framework offers a static method in the string class: String.IsNullOrEmpty.

Syntax Example:
String s;
 
s = "";
//s = null; //Uncomment to test 2nd case.
 
if (String.IsNullOrEmpty(s))
{
  MessageBox.Show("empty string");
}




Logical Operators

[Other Languages] 

Languages Focus

Logical operators perform conditional and, or, and not operations. Some languages support both binary logical operators that link two and unary logical operators negate (make opposite) the truth value of its argument. Finally, some languages short circuit logic. For example, with this or that, if this is an expression returning true, then that is never executed.

Java: 

Java logical operators:

&& and, as in this and that
|| or, as in this or that
! Not, as in Not This
& boolean logical OR (not short circuited)
| boolean logical OR (not short circuited)
?: Ternary (short for if-then-else)
~ Unary bitwise complement
<< Signed left shift
>> Signed right shift
>>> Unsigned right shift
^ Bitwise exclusiv OR

Syntax Example:
//Given expressions a, b, c, and d:
if !((a && b) && (c || d)) {
  //Do something.
}
C#: 

Same as C++ and Java. C# logical operators:

& and, as in this and that No Short Circuit
&& and, as in this and that short circuits
| or, as in this or that No Short Circuit
|| or, as in this or that short circuits
! Not, as in Not This
^ either or, as in this or that but not both

Syntax Example:
//Given expressions a, b, c, and d:
if !((a && b) && (c || d)) 
{
  //Do something.
}




String Concatenation

[Other Languages] 
Java:  "String Concatenation" + or append

In Java, you use either the String concatenation + operator or StringBulder class methods such as append. Since Java compilers frequently create intermediate objects when the + operator is used and don't when StringBuilder.append is used, the append method is faster than the + operator.

In general, use the convenience of a + operator when speed is not an issue. For example, when concatenating a small number of items and when code isn't executed very frequently. A decent rule of thumb is to use the + operator for general purpose programming and then optimize the + operator with StringBuilder.append as needed.

Syntax Example:

Simple + operator example:

System.out.println("Hello" + " " + "Mike.");

 

Using StringBuilder example:

StringBuilder myMsg = new StringBuilder();

myMsg.append("Hello ");
myMsg.append("Mike.");
 
System.out.println(myMsg);
C#:  "String Concatenation" +

C# performs implicit casting of numbers to strings. To concatenate two strings, a string to an integer, or a string to a floating point number, use the + operator. For example, to convert a floating point number to a string just concatenate an empty string to the number as in "" + 3.2.

Alternatively, you can use the System.Text.StringBuilder class which frequently but not always provides faster code.

Syntax Example:
String FirstName;
String LastName;
Int16 Age;
FirstName = "Mike";
LastName = "Prestwood";
Age = 43;
Console.WriteLine(FirstName + " " + LastName + " is " + Age + ".");
  
//Implicit casting of numbers.
//
//This fails:
//MessageBox.Show(3.3);
//
//This works:
MessageBox.Show("" + 3.3); 




Unary Operators

[Other Languages] 

General Info: Unary Operator

An operation with only one operand (a single input). Common unary operators include + plus, - minus, and bitwise not. Some operators can function as both unary and binary operators. For example, + and - operators can serve as either.

Languages Focus

What unary operators are supported in additoin to the standard plus, minus, and bitwise not.

Java: 

An operation with only one operand (a single input). The Java unary operators are ++, --, +, -, ~, and !.

  • + Indicates positive value (numbers are positive without this)
  • - Negates an expression
  • ++ Increment operator by 1
  • -- Decrement operator by 1
  • ! Logical complement operator (inverts the value of a boolean)
  • ~ Bitwise inversion operator (works on integral data types)
More Info / Comment
C#: 

An operation with only one operand (a single input). The following are the C# unary operators: +, -, !, ~, ++, --, true, or false. 





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