Finding max element in Arraylist of integer arrays

Question

I'm attempting to create a function that allows you to pass in a ArrayList and return the max element. I have been unable to figure out a correct solution because of the data type being passed in is not primitive. I've also tried converting the ArrayList to ArrayList without success. Here is my (incorrect) code thus far:

public static void maxArrayListValue(ArrayList<int[]> arrayList) {
    int maxArrayListValue = arrayList.get(0);   // set first arrayList element as highest

    for (int index=1; index < arrayList.size(); index++) {  // cycle through each arrayList element
        if (maxArrayListValue < arrayList.get(index)){      // if new element is > than old element
        maxArrayListValue = arrayList.get(index);           // replace with new maxValue
        maxArrayListIndex = index;                          // record index of max element
        }
    }
    return maxArrayListValue;
}

Any input would be apprecieated.

Elliott Frisch · Accepted Answer · 2014-10-13 01:24:13Z

1

Your method isn't returning anything, and I think you want to iterate the values in each array. Something like,

public static int maxArrayListValue(List<int[]> arrayList) {
    int maxVal = Integer.MIN_VALUE;
    for (int[] arr : arrayList) {
        for (int v : arr) {
            if (v > maxVal) {
                maxVal = v;
            }
        }
    }
    return maxVal;
}

answered Oct 13, 2014 at 1:24

Elliott Frisch

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2 Comments

Thall Over a year ago

This worked perfectly. I just want to make sure I'm understanding this correctly; the first loops through each array in the arraylist and the second loops through each element in each array?

Elliott Frisch Over a year ago

You have a List<int[]> so we first iterate the int[] contents of your List<> and then you have it!

Diego Basch · Accepted Answer · 2014-10-13 01:24:23Z

1

You don't need a loop. Just use java.util.Collections.max(arrayList);

answered Oct 13, 2014 at 1:24

Diego Basch

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2 Comments

Thall Over a year ago

I'm not sure if this works, I thought you could only use collections on primitive data types? I get the error: "The method max(<? extends T>) in the type Collections is not applicable for the arguments (ArrayList<int[]>)".

Diego Basch Over a year ago

If your collection elements don't have a natural ordering, you have to provide a Comparator as the second element.

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