From Script | Spoken-Tutorial
Revision as of 11:48, 17 September 2013 by Sneha
|00:02||Welcome to this spoken tutorial on Logical Operators in Java.|
|00:07||In this tutorial, you will learn about the logical operators|
|00:11||how to check for multiple expressions using logical operators and how to override precedence using parentheses|
|00:20|| For this tutorial we are using
JDK 1.6 and
|00:30||To follow this tutorial you should have knowledge on relational operators in Java|
|00:35||If not, for relevant tutorials, please visit our website as shown.|
|00:40||Logical operators are used to check multiple conditions.|
|00:48||Here is a list of the available logical operators in Java|
|00:54||and, or, not. We shall look into each of them in detail. Switch to Eclipse.|
|01:04||Here We have the Eclipse IDE and the skeleton required for the rest of the code.|
|01:10||We have created a class LogicalOperators and added the main method|
|01:15||Let us create some variables.|
|01:20||boolean b ;|
|01:23||We shall store the result of conditions in b;|
|01:29||int age is equalto 11|
|01:35|| int weight isequalto 42
|01:42||We have the age and weight of a person.|
|01:46|| We shall check if the person is below 18yrs of age and is atleast 40kgs.
|01:52||Let us see how to do so.|
|01:57|| b is equal toage less than 18 ampersand ampersand weight greater than equal to 40
|02:19|| This statement has two expressions and a double ampersand symbol in between.
|02:24|| It checks if age is less than 18 and also if weight is greater than or equal to 40.
|02:31||This operation is called the and operation.|
|02:35|| Let us now print the value b.
|02:40||System dot out dot println(b);|
|02:48||Save and Run|
|02:56|| As we can see, the output is true because both the conditions are satisfied.
|03:02|| Now let us change the weight so that one condition is not satisfied and re run the code.
|03:08|| Change 42 to 32.
|03:14||Save and Run|
|03:21|| the output now is false.
|03:24|| This is because the condition age less than 18 is satisfied
|03:29|| But the condition the weight greater than or equal to 40 is not satisfied
|03:34|| The and operation requires both the conditions to be true for the result to be true.
|03:39||Therefore we get false as our output.|
|03:43||This way, using a double ampersand symbol we can perform and operation.|
|03:53|| Lets say we have age and weight and it is enough if only one of the conditions is satisfied.
|03:59|| In other words, we need to see if the first condition or the second condition is true.
|04:05||It is done using the or operation.|
|04:09|| Let us first remove the earlier condition.
|04:15|| And Type
|04:17|| age less than equal to 15 pipe pipe weight less than equal to 30
|04:35|| There are two conditions and a double pipe symbol in between.
|04:40|| This statement checks if atleast one of the given two conditions is satisfied.
|04:46||Let us run the code to see the output. Save and run|
|04:54||We see that the output is True.|
|04:57||This is because, an or operation, does not need both the conditions to be true like the and operation.|
|05:03||It needs atleast one condition to be true.|
|05:06||So although the condition for weight is not satisfied, since the condition for age is satisfied.|
|05:13||we get the output as true.|
|05:18|| Now let us change the age in such a way that both the conditions are false and see the result.
|05:25|| change 11 to 17
|05:30||Save and Run|
|05:36||Now the output is false because both the conditions are not satisfied.|
|05:41||This way, we use a double PIPE symbol to do an or operation.|
|05:50|| Now let us say we need to check for people who are older than 15 and with weight more than 30kilos.
|05:57||In other words, we need to check the exact opposite of the condition we just did.|
|06:03||In such situations, we use the not operation|
|06:07||First enclose the condition in parentheses.|
|06:17||And Add an exclamation mark before the condition.|
|06:25|| By using an exclamation mark, we check for the exact opposite of the condition inside the parentheses.
|06:32||Since the earlier output was false, now it must true. Let us see|
|06:38|| Save and Run.
|06:44||As we can see, the output is the opposite of earlier one.|
|06:48||This way by using the Exclamation mark we perform not operation. Now Let us say we want people younger than 15.|
|06:58|| Or people younger than 18 and lighter than 40kilos.
|07:04||Let us see how would we go about this condition.|
|07:07||Remove the earlier condition and type|
|07:12||age less than 15|
|07:15||or age less than 18|
|07:24|| and weight less than 40
|07:33|| As we can see, the condition itself is confusing.
|07:36|| Moreover, we do not know if the or operation will be performed first or the and operation.
|07:42|| It depends on the precedence of operators.
|07:46||In such situations, we use parentheses to overwrite the precedence and also make the condition clear.|
|07:53|| So let us add the parentheses.
|08:06||Let us run the code save run|
|08:13|| Now Although the first condition which is age less than 15 is not satisfied,
|08:20|| the second condition, which is,
|08:22|| age less than 18 and weight less than 40 is satisfied.
|08:27||Therefore, output is True.|
|08:30||As a rule, use parentheses to avoid ambiguity and make the expressions clear.|
|08:36||And This how we use the logical operators to check for multiple conditions.|
|08:44||This bring us to the end of this tutorial.|
|08:47||we have learnt about logical operators, how to check for multiple expressions using logical operators and|
|08:54||how to override the precedence using parentheses.|
|09:00||As an assignment for this tutorial,
|09:02||find out if the two expressions, shown are equivalent?|
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|09:52||This tutorial has been contributed by TalentSprint. Thanks for joining.