Rolling Dice

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Complex Decisions

This program uses 3 random numbers to simulate 3 dice rolls.  It repeats the dice rolls 10 times.
Each time the dice are rolled, the program must decide whether 2 of the dice match (as shown in the results above).

if(a==b || b==c || a==c)
{ println( .... "MATCH"); }

This command checks whether dice A matches dice B OR dice B matches dice C OR dice C matches dice A.
The | | symbols stand for "OR".  The  = =  symbol checks whether two numbers are equal.
If a match is detected, then it prints "MATCH".

else
{  println(..... "no match"); }

"Else" means "otherwise".  So if NO match occurs, it prints "no match".

Boolean Logic

George Boole was a mathematician who outlined the basic principles of logical decisions.
A Boolean expression is a series of logical operations that give a result of TRUE or FALSE.
The basic operators in Boolean expressions are OR and AND.

For example, when  a = 4 , b = 5 , c = 4, then

(a == b)    ==>  FALSE
(b == c)    ==>  FALSE
(a == c)    ==>  TRUE

OR expressions
(a == b || b == c )  ==>  FALSE, because neither is true
(a == b || b == c || a == c)  ==>  TRUE, because a == c is true

Whenever a Boolean expression uses OR ( | | ) , only one part must be true to make the whole thing true.

The Java symbol for AND is && .  For example, when a = 4, b = 5, c = 4 , then

 AND expressions
(a == b && b == c )  ==>  FALSE, because both parts are false
(a == b && a == c )  ==>  FALSE, because a == b is false
(a == 4 && c == 4 )  ==>  TRUE, because both parts are true

The following command checks whether two numbers are smaller than 100 and add up to 150.

( a < 100  &&  b < 100  &&  a+b==150 )

Practice

Summary of Symbols

    AND  &&         OR  | |        EQUAL  = =       not Equal   ! =

    Less than or equal     < =        Greater or equal    > =

You should find a summary of Boolean expressions in a Java textbook and study all the possible operations.