There are three issues that distinguish arrays from other types of containers: efficiency, type, and the ability to hold primitives.
The cost of this speed is that the size of an array object is fixed and cannot be changed for the lifetime of that array.
You should generally prefer an ArrayList to an array.
You’ll get a RuntimeException if you exceed the bounds, indicating a programmer error.
Arrays are superior to pre-generic containers because you create an array to hold a specific type.
Arrays are first-class objects
The array identifier is actually a reference to a true object that’s created on the heap. This is the object that holds the references to the other objects.
length member that tells you how many elements can be stored in that array object.
Returning an array
Returning an array is just like returning any other object—it’s a reference.
The garbage collector takes care of cleaning up the array when you’re done with it, and the array will persist for as long as you need it.
Multidimensional arrays
Each vector in the arrays that make up the matrix can be of any length.
The Arrays.deepToString( ) method works with both primitive arrays and object arrays.
Arrays and generics
You cannot instantiate arrays of parameterized types.
Erasure removes the parameter type information, and arrays must know the exact type that they hold, in order to enforce type safety.
You can parameterize the type of the array itself.
The compiler won’t let you instantiate an array of a generic type. However, it will let you create a reference to such an array.
Although you cannot create an actual array object that holds generics, you can create an array of the non-generified type and cast it.
A generic container will virtually always be a better choice than an array of generics.
Creating test data
Arrays.fill()
Since you can only call Arrays.fill( ) with a single data value, the results are not especially useful.
Data Generators
If a tool uses a Generator, you can produce any kind of data via your choice of Generator.
Array Utilities
There are six basic methods in Arrays: equals(), fill(), binarySearch(), sort(), toString(), hashCode().
Copying an array
The Java standard library provides a static method, System.arraycopy( ), which can copy arrays.
If you copy arrays of objects, then only the references get copied—there’s no duplication of the objects themselves.
Comparing arrays
To be equal, the arrays must have the same number of elements, and each element must be equivalent to each corresponding element in the other array, using the equals( ) for each element.
Array element comparisons
You hand a Strategy object to the code that’s always the same, which uses the Strategy to fulfill its algorithm.
sort( ) casts its argument to Comparable.
Sorting an array
The sorting algorithm that’s used in the Java standard library is designed to be optimal for the particular type you’re sorting—a Quicksort for primitives, and a stable merge sort for objects.
Searching a sorted array
If you try to use binarySearchC ) on an unsorted array the results will be unpredictable.
Otherwise, it produces a negative value representing the place that the element should be inserted if you are maintaining the sorted array by hand.
If an array contains duplicate elements, there is no guarantee which of those duplicates will be found.
