This is the most basic decision manage structure. It includes a declare or block of declaration on the “true” course only.

You are watching: The if-then-else statement should be used to write a single alternative decision structure.

*

If the Boolean expression evaluate to true, the statement, or block of statements, that the framework is executed; otherwise, the statements are skipped.

The general kind of the statement is


if (Boolean_Expression) /* A declare or block of explanation */ ;Notice: In PHP, a Boolean expression have to be attached in parentheses.

When only one single statement is supplied in the if statement, you can omit the braces . Thus, the if explain becomes

if (Boolean_Expression) /* One solitary Statement */ ;or friend can also write the statement on one single line, choose this:

if (Boolean_Expression) /* One solitary Statement */;The braces are forced only when an ext than one explain is supplied in the if statement. There is no the braces, PHP can not tell whether a explain is component of the if statement or component of the statements the follow the if statement. Numerous programmers favor to constantly use braces also if the if statement has only one single statement. In both the the following instances the echo $y statement is not component of the if statement.

if ($x == $y) $x++; echo $y;

=if ($x == $y) $x++;echo $y;
Notice: A very common mistake that novice programmers make when writing PHP programs is to confuse the assignment operator v the same operator. They commonly make the mistake of writing if ($x = $y) as soon as they actually want to say if ($x == $y).


Java


if (Boolean_Expression) /* A statement or block of explanation */ ;Notice: In Java, a Boolean expression must be attached in parentheses.

When only one solitary statement is provided in the if statement, you deserve to omit the braces . Thus, the if declare becomes

if (Boolean_Expression) /* One single Statement */ ;or you can also write the explain on one single line, like this:

if (Boolean_Expression) /* One solitary Statement */ ;The braces are forced only when much more than one declare is used in the if statement. Without the braces, Java cannot tell even if it is a statement is part of the if declare or part of the statements the follow the if statement. Countless programmers prefer to constantly use braces also if the if statement consists of only one solitary statement. In both the the following instances the System.out.println(y) statement is not part of the if statement.

if (x == y) x++; System.out.println(y);

=if (x == y) x++;System.out.println(y);
Notice: A an extremely common mistake that novice programmers make once writing Java programs is to confuse the assignment operator v the equal operator. They typically make the mistake of creating if (x = y) once they actually want to say if (x == y).


C++


if (Boolean_Expression) /* A explain or block of statements */ ;Notice: In C++, a Boolean expression need to be enclosed in parentheses.

When only one single statement is used in the if statement, you can omit the braces . Thus, the if statement becomes

if (Boolean_Expression) /* One single Statement */ ;or girlfriend can even write the statement on one single line, choose this:

if (Boolean_Expression) /* One solitary Statement */ ;The braces are compelled only when an ext than one declare is supplied in the if statement. There is no the braces, C++ cannot tell even if it is a explain is part of the if statement or component of the statements the follow the if statement. Countless programmers favor to always use braces also if the if statement includes only one single statement. In both of the following examples the cout explain is not component of the if statement.

if (x == y) x++; cout

=if (x == y) x++;cout
Notice: A an extremely common mistake that novice programmers make as soon as writing C++ programs is to confuse the assignment operator v the equal operator. They typically make the mistake of composing if (x = y) once they actually desire to say if (x == y).


C#


if (Boolean_Expression) /* A declare or block of statements */Notice: In C#, a Boolean expression should be attached in parentheses.

When only one single statement is used in the if statement, you deserve to omit the braces . Thus, the if declare becomes

if (Boolean_Expression) /* One solitary Statement */ ;or girlfriend can also write the statement on one solitary line, like this:

if (Boolean_Expression) /* One single Statement */ ;The braces are compelled only when more than one statement is supplied in the if statement. Without the braces, C# can not tell whether a declare is component of the if explain or part of the statements that follow the if statement. Countless programmers like to always use braces even if the if statement has only one solitary statement. In both of the following examples the Console.Write(y) statement is not component of the if statement.

if (x == y) x++; Console.Write(y);

=if (x == y) x++;Console.Write(y);
Notice: A very common mistake the novice programmers make once writing C# programs is to confuse the assignment operator v the same operator. They commonly make the wrong of creating if (x = y) when they actually desire to say if (x == y).


Visual Basic


If Boolean_Expression then "A explain or block of statementsEnd IfWhen just one solitary statement is provided in the If statement, you have the right to write it on one solitary line, prefer this:

if Boolean_Expression climate "One single Statement

Python


if Boolean_Expression: #A declare or block of statementsNotice: Python was among the first programming languages to force indentation. Python mentions that numerous statements are part of a group by indenting them. The indented team is dubbed a “block the statements” or “code block.” Indentation is considered good practice in other languages, however in Python indentation is mandatory. Code that is component of a block should be indented. For example, every statements that show up inside one if statement should be indented come the ideal by the same variety of spaces; otherwise they are not considered part of the if statement and you probably acquire an error message. There are two basic rules to remember around code blocks’ syntax:

The explain on the first line the a code block constantly ends through a colon ( : ) character.The password underneath the first line need to be indented.

Notice: Python’s official website recommends the use of 4 spaces every indentation level. If you need an ext information you can visit

https://www.python.org/dev/peps/pep-0008.

Notice: In computer system languages other than Python, such as C, C++, C#, Java, or intuitive Basic, indentation is not obligatory but it is quite important in bespeak to do code less complicated to read. It likewise helps programmers to much more easily study and also understand code created by others.

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When just one single statement is supplied in the if statement, you deserve to write that on one single line, prefer this:

if Boolean_Expression: #One solitary StatementNotice: A really common mistake the novice programmers make once writing Python programs is to confuse the assignment operator with the same operator. They typically make the wrong of writing if x = y when lock actually desire to say if x == y.