Difference between revisions of "Java/C2/Logical-Operations/English-timed"

|| '''Time'''

|  In this tutorial, you will learn about the '''logical operators'''.  

|How to check for multiple '''expressions''' using '''logical operators''' and how to '''override''' '''precedence''' using parentheses.

| For this tutorial we are using:

|  To follow this tutorial, you should have knowledge on '''relational operators''' in Java.

| 00:42

| Logical operators are used to check for '''multiple conditions'''.  

| Here is a list of the available '''logical operators''' in Java.

| '''and, or, not'''. We shall look into each of them in detail. Switch to '''Eclipse'''.

|  Here, we have the 'Eclipse IDE' and  the skeleton required for the rest of the code.

| We have created a '''class''' '''LogicalOperators''' and added the '''main method'''.

| Let us '''create''' some '''variables'''.

|  '''boolean b ;'''

 

| We shall store the result of conditions in 'b';

| '''int age''' is equal to 11;  

| '''int weight''' is equal to 42;

| We shall check if the person is below 18yrs of age and is at least 40kgs.

| '''b''' is equal to '''age''' less than '''18''' ampersand ampersand '''weight''' greater than equal to '''40''';

| This statement has two '''expressions''' and a double ampersand symbol in between.  

| It checks if '''age''' is less than '''18''' and also if '''weight''' is greater than or equal to '''40'''.

|  Let us now print the value of 'b'.  

| '''System''' dot '''out''' dot '''println(b);'''

|'''Save '''and '''Run '''.

| Now, let us change the '''weight''' so that one condition is not satisfied and ''re-run'' the code.

| '''Save''' and '''Run'''.  

|  The output now is '''false.'''

| This is because the condition '''age''' less than '''18''' is  satisfied

| but the condition '''weight'''  greater than or equal to '''40''' is not satisfied.

| The '''AND''' operation requires both the conditions to be '''true''' for the result to be '''true.'''

| Therefore we get '''false''' as our output.

| This way, using a  double ampersand symbol we can perform  an '''AND''' operation.

| Let's say we have '''age''' and '''weight''' and it is enough if only one of the conditions is satisfied.

| In other words, we need to see if the first condition or the second condition is '''true.'''

| It is done using the '''OR''' operation.

| And  type:

| '''age''' less than or equal to '''15''' pipe pipe '''weight''' less than or equal to '''30'''

| There are two conditions and a '''double pipe''' symbol in between.

| This statement checks if at least one of the given two conditions is satisfied.

| Let us run the code to see the output. '''Save''' and '''run'''.

|  We see that the output is '''true.'''

|  This is because an '''OR''' operation does not need both the conditions to be true like the '''AND''' operation.

|  It needs at least one condition to be '''true.'''

| So, although the condition for '''weight''' is not satisfied, since the condition for '''age''' is satisfied

| we get the output as '''true.'''

|  Now, let us change the '''age''' in  such a way that both the conditions are false and see the result.

|  change '''11''' to '''17'''.

| '''Save''' and '''Run '''.

| Now the output is '''false''' because both the conditions are not satisfied.

|  This way, we use a double PIPE symbol to do an '''OR''' operation.

|  Now, let us say we need to check for people who are older than 15 and with weight more than 30kilos.

| In such situations, we use the '''NOT''' operation.

|  First, enclose the condition in parentheses.

|  And  add an exclamation mark before the condition.

|  Since the earlier output was '''false''', now it must be   '''true'''. Let us see.

|  This way, by using the exclamation mark we perform the '''NOT''' operation. Now, let us say we want people younger than 15.

| Or people younger than 18 and lighter than 40kilos.

|  Remove the earlier condition and type:  

| '''age''' less than '''15'''

| '''OR''' '''age''' less than '''18 '''

| '''AND''' '''weight''' less than '''40''';

| Moreover, we do not know if the '''OR''' operation will be performed first or the '''AND''' operation.

| It depends on the precedence of '''operators'''.

| So let us add the parentheses.  

| Let us '''run''' the code,  '''save''', '''run'''.  

 

| Now, although the first condition which is '''age''' less than 15 is not satisfied,

|  the second condition which is

| '''age''' less than 18 and '''weight''' less than 40 is satisfied.

| Therefore, the output is '''true'''.

| As a rule, use parentheses to avoid ambiguity and make the '''expressions''' clear.

|  | And  this is how we use the logical operators to check for multiple conditions.

|  This brings us to the end of the tutorial.  

|  We have learnt about '''logical operators''', how to check for multiple '''expressions''' using '''logical operators '''and  

| how to '''override''' the precedence using parentheses.

| find out if the two expressions shown are equivalent?

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