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是否允許在Java中使用以下代碼？我的程序不起作用，除非我將此行註釋掉，而且我不確定是否允許在if中使用多個& &語句。Java中允許多個&&語句？
if(number.isBusy() && number2.isBusy() && number3.isBusy() && number4.isBusy() && number5.isBusy()) {}
編輯補充： 如果您註釋掉上面給出的行，程序將實際顯示在輸出窗口的東西（雖然那得到的東西加入到它的唯一的事情就是「5號」），如果它被留下，所有的輸出都是零。
這是整個程序現在：
// FILE: Line.java
// This program illustrates the use of the lineSimulate method which uses
// a simple queue to simulate cars waiting at a car wash.
import java.util.LinkedList;
import java.util.Queue;
import java.util.Scanner;
// import edu.colorado.simulations.BooleanSource;
// import edu.colorado.simulations.Line ;
// import edu.colorado.simulations.Averager;
/******************************************************************************
* The <CODE>CarWash</CODE> Java application illustrates the use of
* the <CODE>lineSimulate</CODE> method.
* The illustration uses the following values:
* <CODE>
* <br>lineTime = 240
* <br>arrivalTime = 0.0025
* <br>totalTime = 6000
* </CODE>
*
* <p><dt><b>Java Source Code for this class:</b><dd>
* <A HREF="../applications/CarWash.java">
* http://www.cs.colorado.edu/~main/applications/CarWash.java
* </A>
*
* @author Michael Main
* <A HREF="mailto:[email protected]"> ([email protected]) </A>
*
* @version
* Jun 12, 1998
******************************************************************************/
public class LineWait
{
/**
* The main method activates <CODE>lineSimulate</CODE> with the values:
* <CODE>
* <br>lineTime = 240
* <br>arrivalTime = 0.0025
* <br>totalTime = 6000
* </CODE>
* <BR>The <CODE>String</CODE> argument (<CODE>args</CODE>) is not used in
* this implementation.
**/
public static void main(String[ ] args)
{
final int LINETIME = 100 + (int)(Math.random() * ((400) + 1));
final double ARRIVALPROB = (Math.random() * ((.1) + 1));
final int TOTALTIME = 6000;
lineSimulate(LINETIME, ARRIVALPROB, TOTALTIME);
}
/**
* Simulate the running of a car washer for a specified amount of time.
* @param <CODE>lineTime</CODE>
* the number of seconds required to wash one car
* @param <CODE>arrivalProb</CODE>
* the probability of a customer arriving in any second, for example
* 0.1 is 10%
* @param <CODE>totalTime</CODE>
* the total number of seconds for the simulation
* <dt><b>Precondition:</b><dd>
* <CODE>lineTime</CODE> and <CODE>totalTime</CODE> are positive;
* <CODE>arrivalProb</CODE> lies in the range 0 to 1.
* <dt><b>Postcondition:</b><dd>
* The method has simulated a car wash where <CODE>lineTime</CODE> is the
* number of seconds needed to wash one car, <CODE>arrivalProb</CODE> is
* the probability of a customer arriving in any second, and
* <CODE>totalTime</CODE> is the total number of seconds for the
* simulation. Before the simulation, the method has written its three
* parameters to <CODE>System.out</CODE>. After the simulation, the method
* has written two pieces of information to <CODE>System.out</CODE>:
* (1) The number of cars washed, and (2) The average waiting time for
* customers that had their cars washed. (Customers that are still in the
* queue are not included in this average).
* @exception java.lang.IllegalArgumentException
* Indicates that one of the arguments violates the precondition.
**/
public static void lineSimulate
(int lineTime, double arrivalProb, int totalTime)
{
Queue<Integer> arrivalTimes = new LinkedList<Integer>();
Queue<Integer> arrivalTimes2 = new LinkedList<Integer>();
Queue<Integer> arrivalTimes3 = new LinkedList<Integer>();
Queue<Integer> arrivalTimes4 = new LinkedList<Integer>();
Queue<Integer> arrivalTimes5 = new LinkedList<Integer>();
int next;
BooleanSource arrival = new BooleanSource(arrivalProb);
Line number = new Line(lineTime);
Line number2 = new Line(lineTime);
Line number3 = new Line(lineTime);
Line number4 = new Line(lineTime);
Line number5 = new Line(lineTime);
Averager waitTimes = new Averager();
Averager waitTimes2 = new Averager();
Averager waitTimes3 = new Averager();
Averager waitTimes4 = new Averager();
Averager waitTimes5 = new Averager();
int currentSecond;
// Write the parameters to System.out.
System.out.println("Seconds to wait in line " + lineTime);
System.out.print("Probability of customer arrival during a second: ");
System.out.println(arrivalProb);
System.out.println("Total simulation seconds: " + totalTime);
// Check the precondition:
if (lineTime <= 0 || arrivalProb < 0 || arrivalProb > 1 || totalTime < 0)
throw new IllegalArgumentException("Values out of range");
for (currentSecond = 0; currentSecond < totalTime; currentSecond++)
{ // Simulate the passage of one second of time.
// Check whether a new customer has arrived.
if (arrival.query())
{
System.out.println("Test1");
if(number.isBusy() && number2.isBusy() && number3.isBusy() && number4.isBusy() && number5.isBusy())
{
System.out.println("Test2");
if(arrivalTimes.size() < arrivalTimes2.size() && arrivalTimes.size() < arrivalTimes3.size() && arrivalTimes.size() < arrivalTimes4.size() && arrivalTimes.size() < arrivalTimes5.size())
{
arrivalTimes.add(currentSecond);
System.out.println("Test");
}
else if(arrivalTimes2.size() < arrivalTimes.size() && arrivalTimes2.size() < arrivalTimes3.size() && arrivalTimes2.size() < arrivalTimes4.size() && arrivalTimes2.size() < arrivalTimes5.size())
{
arrivalTimes2.add(currentSecond);
System.out.println("Test");
}
else if(arrivalTimes3.size() < arrivalTimes.size() && arrivalTimes3.size() < arrivalTimes2.size() && arrivalTimes3.size() < arrivalTimes4.size() && arrivalTimes3.size() < arrivalTimes5.size())
{
arrivalTimes3.add(currentSecond);
System.out.println("Test");
}
else if(arrivalTimes4.size() < arrivalTimes.size() && arrivalTimes4.size() < arrivalTimes3.size() && arrivalTimes4.size() < arrivalTimes2.size() && arrivalTimes4.size() < arrivalTimes5.size())
{
arrivalTimes4.add(currentSecond);
System.out.println("Test");
}
else{arrivalTimes5.add(currentSecond);}
}
}
// Check whether we can put the person into a line.
if ((!number.isBusy()) && (!arrivalTimes.isEmpty()))
{
next = arrivalTimes.remove();
waitTimes.addNumber(currentSecond - next);
number.startMoving();
}
if ((!number2.isBusy()) && (!arrivalTimes2.isEmpty()))
{
next = arrivalTimes2.remove();
waitTimes2.addNumber(currentSecond - next);
number2.startMoving();
}
if ((!number3.isBusy()) && (!arrivalTimes3.isEmpty()))
{
next = arrivalTimes3.remove();
waitTimes3.addNumber(currentSecond - next);
number3.startMoving();
}
if ((!number4.isBusy()) && (!arrivalTimes4.isEmpty()))
{
next = arrivalTimes4.remove();
waitTimes4.addNumber(currentSecond - next);
number4.startMoving();
}
if ((!number5.isBusy()) && (!arrivalTimes5.isEmpty()))
{
next = arrivalTimes5.remove();
waitTimes5.addNumber(currentSecond - next);
number5.startMoving();
}
// Subtract one second from the remaining time in the current li
number.reduceRemainingTime();
number2.reduceRemainingTime();
number3.reduceRemainingTime();
number4.reduceRemainingTime();
number5.reduceRemainingTime();
}
// Write the summary information about the simulation.
System.out.println("\nCustomers served Line1: " + waitTimes.howManyNumbers());
if (waitTimes.howManyNumbers() > 0)
System.out.println("Average wait Line1: " + waitTimes.average() + " sec");
System.out.println("\nCustomers served Line2: " + waitTimes2.howManyNumbers());
if (waitTimes.howManyNumbers() > 0)
System.out.println("Average wait Line2: " + waitTimes2.average() + " sec");
System.out.println("\nCustomers served Line3: " + waitTimes3.howManyNumbers());
if (waitTimes.howManyNumbers() > 0)
System.out.println("Average wait Line3: " + waitTimes3.average() + " sec");
System.out.println("\nCustomers served Line4: " + waitTimes4.howManyNumbers());
if (waitTimes.howManyNumbers() > 0)
System.out.println("Average wait Line4: " + waitTimes4.average() + " sec");
System.out.println("\nCustomers served Line5: " + waitTimes5.howManyNumbers());
if (waitTimes.howManyNumbers() > 0)
System.out.println("Average wait Line5: " + waitTimes5.average() + " sec");
}
}
這是允許的。你能擴展「不行」嗎？ – 2012-04-02 03:56:40
是...... – 2012-04-02 03:56:54
定義'不起作用'。大概你已經確定它編譯了，但這也意味着它是合法的Java。 – EJP 2012-04-02 04:00:30