How would I switch from an Array to an ArrayList?

 

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  • Create ArrayList from array 32 answers

    • To change code that uses an array into code that uses an ArrayList :

  • Instead of a[i] , when it's not on the left side of an assignment, use a.get(i)

  • Instead of a.length , use a.size()

  • Instead of setting a[i] = expression : if i is known to be in range (0 <= i <= a.length-1 ), use a.set(i, expression) . If i == a.length , you couldn't use a[i] = expression with an array, but you can do it with an ArrayList , increasing the size by 1: a.add(expression) . If i > a.length , so that you want to add a new element in the ArrayList leaving a gap, then something like: 

    while (a.size() < i)
    a.add (null);
// at this point a.size == i
a.add (expression);
// now a.size == i+1

    • That should cover all the basic operations on arrays. There are some utility operations defined in Arrays that don't have equivalent operations in ArrayList , like binarySearch .

    I use LinkedList, it's very similar to ArrayList. You declare it like this:

    LinkedList<Student> StudentList = new LinkedList<Student>();

    Then you can add students like this: 

    StudentList.add(newStudent(id,name,major,gpa,campus,address,number,email,current,past,future,notes))

    Then you can remove students like this: 

    StudentList.remove(Student student1);

    You can also clear all the students from the list,if needed, like this: 

    StudentsList.clear();

    Hope this helps!

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