Difference between revisions of "The If-Else Statement"
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− | {{Template:1010Topic|Chapter_TOC=[[Control Structures]]|Introduction=To further your knoledge on if-statments we will now add the else part to the if-statements. If-Else Statements add the element that if the conditions are false then "do" somthing else.}} | + | {{Template:1010Topic|Chapter_TOC=[[Control Structures]]|Introduction=To further your knoledge on if-statments we will now add the else part to the if-statements. If-Else Statements add the element that if the conditions are false then "do" somthing else.|Overview=This section covers if-else-statements and how they increace functionallity of the if-statement and how and when to use them.}} |
==The If-Else Statement== | ==The If-Else Statement== |
Revision as of 15:41, 20 March 2007
COMP 1010 Home > Control Structures
IntroductionTo further your knoledge on if-statments we will now add the else part to the if-statements. If-Else Statements add the element that if the conditions are false then "do" somthing else.
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The If-Else Statement
Sometimes it is not sufficient to simply tell the computer "If such-and-such condition is true do this". Somtimes you will want to say "If such-and-such is true do this, otherwise do that". A simple way of doing this would be to have a separate if-statement that will return the opposite value of the first:
if (number%2 == 0) { System.out.println("The number is even"); }//if if (number%2 !=0) { System.out.println("The number is odd"); }//if
While this approach works, it is needlessly complicated; there is a better way of doing the same task, but with less work. The keyword else can be used to tell the computer do execute a different body of code if the condition of an if-statement returns false. We can rewrite the code from above to take advantage of this keyword like this:
if (number%2 == 0) { System.out.println("The number is even"); }//if else { System.out.println("The number is odd"); }//else
If we step through this last example the computer will evaluate the condition number%2 == 0 and check the result. If the result is true the body of the if-statement will be executed, just like in the previous examples. If the result is false then the body of the else-statement is executed.
The keyword else and the corresponding body form what is called an else-block or else-statement. It is very important to note that an else-block is always associated with an if-block, and each if-block can only ever be associated with zero or one else-blocks.
Together the keywords if, else, the condition, and the two bodies form a code-block known as an if-else block or if-else statement.
Anatomy of the If-Else Statement
The if-else statement is made up of the following parts:
- the keyword if
- the condition
- the body of the if-statement
- the keyword else
- the body of the else-statement
The general form of an if-else statement is:
if (condition) { code to execute if condition == true } else { code to execute if condition == false }