Java/C2/Logical-Operations/English-timed

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.
00:42	Logical operators are used to check for 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 equal to 11;
01:35	int weight is equal to 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 at least 40kgs.
01:52	Let us see how to do so.
01:57	b is equal to age 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 of '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 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 an AND operation.
03:53	Let's 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 or equal to 15 pipe pipe weight less than or equal to 30
04:35	There are two conditions and a double pipe symbol in between.
04:40	This statement checks if at least 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 at least 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 be 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 the 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, the output is true.
08:30	As a rule, use parentheses to avoid ambiguity and make the expressions clear.
08:36	And this is how we use the logical operators to check for multiple conditions.
08:44	This brings us to the end of the 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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Contributors and Content Editors

Gaurav, Kavita salve, PoojaMoolya, Priyacst, Sandhya.np14, Sneha