Java - get element position in array

Question

I\'m familiar with the ways I can get an element position in array, especially the ones showed here: Element position in array

But my problem is I can\'t figure out

Answer 1

just use the call listPackages.indexOf(current_package);

ArrayList.contains(Object o) calls indexOf(Object o) internally in ArrayList:

/**
 * Returns true if this list contains the specified element.
 * More formally, returns true if and only if this list contains
 * at least one element e such that
 * (o==null ? e==null : o.equals(e)).
 *
 * @param o element whose presence in this list is to be tested
 * @return true if this list contains the specified element
 */
public boolean contains(Object o) {
return indexOf(o) >= 0;
}