check the values of the arraylist values in java

Question

I'm trying to write a method that checks weather all the Objects in an ArrayList have the same value. For example, in the following code list1 should return true, and list2 should return false...

list1=[2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2]
list2=[1,3,4,2,4,1,3,4,5,6,2,1,5,2,4,1]

What is the best way to write this method? Is there any quick methods to do this, or do I need to manually loop through the values?

Alexander Pavlov · Accepted Answer · 2012-04-17 15:45:56Z

2

So, you need to check if all the values in a list are the same?

boolean checkList(List<Integer> list) {
  if (list.isEmpty())
    return false;

  int value = list.get(0);
  for (int i = 1; i < list.size(); ++i) {
    if (list.get(i) != value)
      return false;
  }

  return true;
}

but I'd be careful about null values in the list, too...

answered Apr 17, 2012 at 15:45

Alexander Pavlov

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4 Comments

Colin Hebert Over a year ago

You should start your for at 0. It's not an useful check but it's better than returning false if there is only one value in the List

Alexander Pavlov Over a year ago

If there is only one element in the list, the for block is not executed and true is returned.

Alexander Pavlov Over a year ago

The i < list.size() condition will not let it run (1 < 1 is false). Anyway, you can try it out in your IDE.

Alexander Pavlov Over a year ago

Glad I still remember some Java :)

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