tailieunhanh - Lecter Java: Program design - Chapter 6: Iteration

In this chapter, we consider the while, for, and do-while looping constructs that control how many times a statement list is iterated (executed). Loops make programs much more powerful and capable of solving significant problems. Mastering the design and implementation of loops is an important part of a programmer's education. | Iteration Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Java looping Options while do-while for Allow programs to control how many times a statement list is executed Averaging Problem Extract a list of positive numbers from standard input and produce their average Numbers are one per line A negative number acts as a sentinel to indicate that there are no more numbers to process Observations Cannot supply sufficient code using just assignments and conditional constructs to solve the problem Don’t how big of a list to process Need ability to repeat code as needed Averaging Problem Extract a list of positive numbers from standard input and produce their average Numbers are one per line A negative number acts as a sentinel to indicate that there are no more numbers to process Algorithm Prepare for processing Get first input While there is an input to process do { Process current input Get the next input } Perform final processing Averaging . | Iteration Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Java looping Options while do-while for Allow programs to control how many times a statement list is executed Averaging Problem Extract a list of positive numbers from standard input and produce their average Numbers are one per line A negative number acts as a sentinel to indicate that there are no more numbers to process Observations Cannot supply sufficient code using just assignments and conditional constructs to solve the problem Don’t how big of a list to process Need ability to repeat code as needed Averaging Problem Extract a list of positive numbers from standard input and produce their average Numbers are one per line A negative number acts as a sentinel to indicate that there are no more numbers to process Algorithm Prepare for processing Get first input While there is an input to process do { Process current input Get the next input } Perform final processing Averaging Problem Extract a list of positive numbers from standard input and produce their average Numbers are one per line A negative number acts as a sentinel to indicate that there are no more numbers to process Sample run Enter positive numbers one per line. Indicate end of list with a negative number. -1 Average public class NumberAverage { // main(): application entry point public static void main(String[] args) throws IOException { // set up the list processing // prompt user for values // get first value // process values one-by-one while (value >= 0) { // add value to running total // processed another value // prepare next iteration - get next value } // display result if (valuesProcessed > 0) // compute and display average else // indicate no average to display } } Roadmap for program ("Enter positive numbers 1 per line.\n" + "Indicate end of the list with a negative number."); Scanner stdin = new Scanner(); int valuesProcessed = 0; double .