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Java greenhorn adding random numbers  RSS feed

 
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Please help I am trying to get x below to equal the sum of the first two random integers and not integers 3 and 4. But the program doesn't add togetehr -7 and 12 but instead adds together later random integers that are created to get an answer of 14. What do I need to do? Thanks for any assistance. This is my first time using JAVA and I am struggling.

int rand_int1 = -rand.nextInt(20);
       int rand_int2 = rand.nextInt(20);
       int x;
       x = (-rand.nextInt(20) + rand.nextInt(20));
       System.out.println("Answer is: "+x);
               System.out.println("Add this number: "+rand_int1);
       System.out.println("and this number together: "+rand_int2);

run:
Answer is: 14
Add this number: -7
and this number together: 12
BUILD SUCCESSFUL (total time: 0 seconds)

The program will be used to create 20 random integers once it is fully written but I am not able to get the first random numbers to be used in the program.

 
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Phil Bignell wrote:Please help I am trying to get x below to equal the sum of the first two random integers and not integers 3 and 4. But the program doesn't add togetehr -7 and 12 but instead adds together later random integers that are created to get an answer of 14. What do I need to do? Thanks for any assistance. This is my first time using JAVA and I am struggling.

int rand_int1 = -rand.nextInt(20);
       int rand_int2 = rand.nextInt(20);
       int x;
       x = (-rand.nextInt(20) + rand.nextInt(20));
       System.out.println("Answer is: "+x);
               System.out.println("Add this number: "+rand_int1);
       System.out.println("and this number together: "+rand_int2);

run:
Answer is: 14
Add this number: -7
and this number together: 12
BUILD SUCCESSFUL (total time: 0 seconds)



Why are you calling rand.nextInt(...) four times? You only need to call it two times.
 
Phil Bignell
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I am later using this to produce 20 random numbers but first want to do calculations with each pair of random numbers.
 
Phil Bignell
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I assume you mean I call it four times as I use four numbers. If I just want to add 2 numbers together then I assume that I just use   rand.nextInt(2)


Could I then loop through 5 times to get 20 numbers?
 
Gerard Gauthier
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Phil Bignell wrote:I assume you mean I call it four times as I use four numbers. If I just want to add 2 numbers together then I assume that I just use   rand.nextInt(2)


Could I then loop through 5 times to get 20 numbers?



To address your original problem... Won't this do what you want?
 
Gerard Gauthier
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If you need 20 random numbers, why don't you create an array of integers and populate it with random numbers.. example:

 
Phil Bignell
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Thank you for your reply showing how to get 20 random integers in the array. How though can I refer to each integer in the array so I can do separate calculations on each pair of integers?
 
Gerard Gauthier
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Phil Bignell wrote:Thank you for your reply showing how to get 20 random integers in the array. How though can I refer to each integer in the array so I can do separate calculations on each pair of integers?



Just use a for loop and make sure you increment by 2 since you are grabbing a pair of entries.
 
Phil Bignell
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Gerard Thank you for your help with this.
 
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Gerard Gauthier wrote:. . .

Ouch! I don't like that at all. I think both of you are confusing the range of the number obtained and how many you are getting. Please have a look at the documentation for Random#nextInt(). Look what the argument passed means, and how many numbers you get, and what range they are in. Also look at this method and other methods with similar names. That returns an IntStream, which has a method directly producing an int[]. You can get a 1000‑element array containing ints, none less than −100 and all less than 100, like this:-You refer to the elements by the usual technique: randoms[i]
 
Phil Bignell
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Campbell Thanks I will look through the material..

 
Campbell Ritchie
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Phil Bignell wrote:Campbell Thanks

That's a pleasure

I will look through the material..

Make sure to have a good look at it; you will find that technique very useful.
 
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