Difference between revisions of "Java/C2/Logical-Operations/English-timed"
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| − | | '''how to check for multiple expressions using logical operators''' and '''how to | + | | '''how to check for multiple expressions using logical operators''' and '''how to override precedence using parentheses''' |
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Revision as of 11:48, 17 September 2013
| Time' | Narration |
| 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
Ubuntu 11.10, JDK 1.6 and Eclipse 3.7 |
| 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? |
| 09:10 | To know more about the Spoken Tutorial project, watch the video available at the following link, It summarises the Spoken Tutorialproject. |
| 09:18 | if you do not have good bandwidth, you can download and watch it |
| 09:23 | The Spoken Tutorial Project Team. Conducts workshops using spoken tutorials and gives certificates for those who pass an online test. |
| 09:30 | For more details, please write to contact AT spoken HYPHEN tutorial DOT org. |
| 09:36 | Spoken Tutorial Project is a part of the Talk to a Teacher project |
| 09:40 | It is supported by the National Mission on Education through ICT, MHRD, Government of India. |
| 09:46 | More information on this Mission is available at the following link spoken HYPHEN tutorial DOT org SLASH NMEICT HYPHEN Intro |
| 09:52 | This tutorial has been contributed by TalentSprint. Thanks for joining.
|
Contributors and Content Editors
Gaurav, Kavita salve, PoojaMoolya, Priyacst, Sandhya.np14, Sneha
