Arrays and ArrayLists - Java: How to Program Early Objects - page 287

be copied. The second argument ( 0 ) is the index that specifies the starting point in the
range of elements to copy from the array. This value can be any valid array index. The
third argument ( intArrayCopy ) specifies the destination array that will store the copy. The
fourth argument ( 0 ) specifies the index in the destination array where the first copied ele-
ment should be stored . The last argument specifies the number of elements to copy from the
array in the first argument. In this case, we copy all the elements in the array.
Lines 30 and 35 call static method equals of class Arrays to determine whether all
the elements of two arrays are equivalent. If the arrays contain the same elements in the
same order, the method returns true ; otherwise, it returns false .
Error-Prevention Tip 7.3
When comparing array contents, always use Arrays.equals(array1, array2) , which
compares the two arrays' contents, rather than array1.equals(array2) , which compares
whether array1 and array2 refer to the same array object.
Lines 40 and 49 call static method binarySearch of class Arrays to perform a
binary search on intArray , using the second argument ( 5 and 8763 , respectively) as the
key. If value is found, binarySearch returns the index of the element; otherwise, bina-
rySearch returns a negative value. The negative value returned is based on the search key's
insertion point —the index where the key would be inserted in the array if we were per-
forming an insert operation. After binarySearch determines the insertion point, it
changes its sign to negative and subtracts 1 to obtain the return value. For example, in
Fig. 7.22, the insertion point for the value 8763 is the element with index 6 in the array.
Method binarySearch changes the insertion point to -6 , subtracts 1 from it and returns
the value -7 . Subtracting 1 from the insertion point guarantees that method binarySearch
returns positive values (>= 0) if and only if the key is found. This return value is useful for
inserting elements in a sorted array. Chapter 19 discusses binary searching in detail.
Common Programming Error 7.6
Passing an unsorted array to binarySearch is a logic error—the value returned is unde-
fined.
Java SE 8—Class Arrays Method parallelSort
The Arrays class now has several new “parallel” methods that take advantage of multi-core
hardware. Arrays method parallelSort can sort large arrays more efficiently on multi-
core systems. In Section 23.12, we create a very large array and use features of the
Java SE 8 Date/Time API to compare how long it takes to sort the array with methods
sort and parallelSort .
7.16 Introduction to Collections and Class ArrayList
The Java API provides several predefined data structures, called collections , used to store
groups of related objects in memory. These classes provide efficient methods that organize,
store and retrieve your data without requiring knowledge of how the data is being stored .
This reduces application-development time.
You've used arrays to store sequences of objects. Arrays do not automatically change
their size at execution time to accommodate additional elements. The collection class