i need to find a integer data in arraylist?

问题

I have an Arraylist. If user enter the same number secondly I want to show to user. For this I need to find Arraylist have it or not.

I hope I made myself clear.

回答1:

If you are checking to see if some value is stored in an ArrayList you can use the contains() method, this will return true if the object is in the list, false otherwise.

ArrayList<Integer> intList = new ArrayList<>();

intList.add(5);
intList.add(7);
intList.add(3);
intList.add(-2);

intList.contains(-1); //returns false
intList.contains(3); //returns true

回答2:

You might want to use ArrayList.contains() to check if the element is in the ArrayList or not.

回答3:

No, you have not. But here's my best guess:

List<Integer> values = Arrays.asList( 1, 2, 4, -5, 44 );
int userValue = 44;
if (!values.contains(userValue)) {
    values.add(userValue);
}

回答4:

If I understand your question, you want to check if an array list already contains and integer value. If so, you could use ArrayList.contains().

Sample code here:

ArrayList list = new ArrayList();
int x = 4, y = 7;
int z = x;

list.add(x);

//List contains the value 4, which is the value stored in z
//Program will output "List contains 4"
if(list.contains(z))
{
    System.out.printf("List contains %d\n", z);
}
else
{
    System.out.printf("List does not contain %d\n", z);
}

//List contains the value 7, which is the value stored in y
//Program will output "List does not contain 7"   
if(list.contains(y))
{
    System.out.printf("List contains %d\n", y);
}
else
{
    System.out.printf("List does not contain %d\n", y);
}

来源：https://stackoverflow.com/questions/9342859/i-need-to-find-a-integer-data-in-arraylist

标签

java

arraylist