Apex Random Select & Display

Question

Apex Random Select & Display

• I have an object named Parts__c.
• Parts__c has 2 fields: ABC_Code__c and Parts_Number__c.
• ABC_Code__c is type text and its value range is A, B, or C.
• Parts_Number__c is type Autonumber.
• Object Parts__c has 50 records: 5 A's, 15 B's, and 30 C's.

I need help writing an Apex class that grabs only the C's and randomly lists them each time they're selected.

Answer 1

You'd probably do something like this - get the records:

Parts__c[] parts = [Select ABC_Code__c, Parts_Number__c From Parts__c Where ABC_Code = 'C'];

Now to randomize, you'll want to loop this list grabbing items randomly and putting them into another list.

First define a function to get a random number based on a supplied max:

public Integer randomWithMax(Integer max){
    Integer rand = Math.round(Math.random()*1000);
    return Math.mod(rand, max);
}

Then loop:

Integer listSize = parts.size();
Integer initialSize = listSize;
Parts__c randomParts = new Parts__c[]{};

for (Integer i = 0 ; i < initialSize ; i++ ){
    Integer rand = randomWithMax(listSize);
    Parts__c part = parts[rand];
    randomParts.add(part);
    parts.remove(rand);
    listSize --;
}

Answer 2

I know this is an old thread, but I was trying to figure this out yesterday, and want to share another option that I think solves this. This is for some code that simulates dealing 25 random cards from a deck. I added random numbers to a List at the same time that I added them to a Map, then I sorted the List and used the first 25 values as keys to pull cards from the Map.

public List<Card__c> drawRandomCards() {
    List<Card__c> selectedCards = new List<Card__c>();
    List<Card__c> allCards = [SELECT Id, Name from Card__c];
    Decimal randNum = 0;
    List<Decimal> randNums = new List<Decimal>();
    Map<Decimal,Card__c> randNumsToCards = new Map<Decimal,Card__c>();

    for(Card__c card : allCards) {
        randNum = Math.random();
        randNums.add(randNum);
        randNumsToCards.put(randNum,card);
    }

    randNums.sort();

    for (Integer i=0; i<25; i++) {
        selectedCards.add(randNumsToCards.get(randNums[i]));
    }

    return selectedCards;
}

Answer 3

I figured it out. Thanks for the response. I used a nested for loop, and a random generator, to randomly grab elements from List1, sequentially assign them to List2, and then print List2 using VisualForce.

public sortController()
{
    sortparts=[SELECT ABC_Code__c, Name FROM sm1e_smPart__c WHERE ABC_Code__c = 'C'];  
    count = (integer)aggResult[0].get('expr0'); //Convert number of Cs to integer
    randomized = new List<sm1e_smPart__c>(count);
    for(Integer i = 0; i < count; i++)
    {
        for(Integer j = 0; j < count; j++)
        {
            Integer rand = Math.round(Math.random()*1000);
            while(rand > count-1){rand = Math.round(Math.random()*1000);}
            randomized[j] = sortparts[rand];
        }
    }
}