Java How to Program Fourth Edition - DCC

332 Arrays Chapter 7
Fig. Fig. 7.10 7.10 Passing arrays and individual array elements to methods (part 3 of 3).
Next, the program demonstrates that individual elements of primitive-type arrays are
passed to methods by value. To show the value of array[ 3 ] before calling method
modifyElement, lines 37–39 append the value of array[ 3 ] (and other information)
to output. Line 42 invokes method modifyElement and passes array[ 3 ] as an
argument. Remember that array[ 3 ] is actually one int value in array. Also,
remember that values of primitive types are passed to methods by value. Therefore, the program
passes a copy of array[ 3 ]. Method modifyElement multiplies its argument
by 2 and stores the result in its parameter element. Method parameters are local variables,
so when modifyElement terminates, the local variable element is destroyed.
Thus, when the program returns control to init, line 44 appends the unmodified value of
array[ 3 ] output. Line 45 displays the results in the JTextArea.
7.7 Sorting Arrays
Sorting data (i.e., placing the data into some particular order such as ascending or descending)
is one of the most important computing applications. A bank sorts all checks by account number
so that it can prepare individual bank statements at the end of each month. Telephone
companies sort their lists of accounts by last name and, within that, by first name, to make it
easy to find phone numbers. Virtually every organization must sort some data and in many
cases massive amounts of data. Sorting data is an intriguing problem that has attracted some
of the most intense research efforts in the field of computer science. In this chapter, we discuss
one of the simplest sorting schemes. In the exercises in this chapter, Chapter 19 and
Chapter 21, we investigate more complex schemes that yield superior performance.
Performance Tip 7.3
Sometimes, the simplest algorithms perform poorly. Their virtue is that they are easy to program,
test and debug. Sometimes, more complex algorithms are required to realize maximum
performance. 7.3
Figure 7.11 sorts the values of array (a the 10-element array of int values) into
ascending order. The technique we use is called the bubble sort or the sinking sort, because
the smaller values gradually “bubble” their way to the top of the array (i.e., toward the first
element) like air bubbles rising in water, while the larger values sink to the bottom (end) of
the array. The technique uses nested loops to make several passes through the array. Each
pass compares successive pairs of elements. If a pair is in increasing order (or the values
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