Generics and the ArrayList Class - Absolute Java - page 769

Display 14.1 Some Methods in the Class ArrayList (part 3 of 3)

public int indexOf(Object target)
Returns the index of the first element that is equal to target . Uses the method equals of the
object target to test for equality. Returns —1 if target is not found.

public int lastIndexOf(Object target)
Returns the index of the last element that is equal to target . Uses the method equals of the
object target to test for equality. Returns - 1 if target is not found.

MEMORY MANAGEMENT (SIZE AND CAPACITY)
public boolean isEmpty()
Returns true if the calling ArrayList is empty (that is, has size 0 ); otherwise, returns false .

public int size()
Returns the number of elements in the calling ArrayList .

public void ensureCapacity( int newCapacity)
Increases the capacity of the calling ArrayList , if necessary, in order to ensure that
the ArrayList can hold at least newCapacity elements. Using ensureCapacity can
sometimes increase efficiency, but its use is not needed for any other reason.

public void trimToSize()
Trims the capacity of the calling ArrayList to the ArrayList 's current size. This method is
used to save storage space.

MAKE A COPY
public Object[] toArray()
Returns an array containing all the elements on the list. Preserves the order of the elements.

public Type [] toArray( Type [] a)
Returns an array containing all the elements on the list. Preserves the order of the elements. Type can
be any class types. If the list will fit in a , the elements are copied to a and a is returned. Any elements
of a not needed for list elements are set to null . If the list will not fit in a , a new array is created.
(As we will discuss in Section 14.2, the correct Java syntax for this method heading is
public <Type> Type[] toArray( Type[] a)
However, at this point we have not yet explained this kind of type parameter syntax.)

public Object clone()
Returns a shallow copy of the calling ArrayList . Warning : The clone is not an independent copy.
Subsequent changes to the clone may affect the calling object and vice versa. (See Chapter 5 for a
discussion of shallow copy.)

EQUALITY
public boolean equals(Object other)
If other is another ArrayList (of any base type), then equals returns true if, and only if,
both ArrayList s are of the same size and contain the same list of elements in the same order.
(In fact, if other is any kind of list , then equals returns true if, and only if, both the calling
ArrayList and other are of the same size and contain the same list of elements in the same
order. Lists are discussed in Chapter 16.)