Not sure why this is not working

问题:

This is a program i'm stuck on for school. Can't figure out why it won't give me a average and a greatest. The program runs 50 times like i want it to but does not add a value to moves and total.

import java.util.*;

public class RandomWalk {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Random rand = new Random();

        int location;
        double average;
        int greatest=0;
        int moves = 0;
        int total = 0;
        int step;

        for (int i = 0; i < 50; i++) {

            location = 4;
            step = rand.nextInt((2 - 1) + 1) + 1;


            while (location < 1 || location > 7) {
                moves ++;
                if (step == 2){
                    location ++;    
                } else {
                    location --;
                }
                if (moves > greatest) {
                    greatest = moves;
                    total += moves;
                }
            }
        }

        average = total / 50;

        System.out.println("The greatest number of steps: " + greatest);
        System.out.println("The average number of steps:  " + average);

     }

}

fixed the for loop but it still does not give me the average and the greatest.

as for the while (location < 1 || location > 7) it should run till the person stands on location 1 or location 7.

here is the problem i was given:

In the "random walk", a person is placed at the center of a seven meter long bridge. Each step moves a person 1 meter either forward or backward at random. Create a randomwalk that determines how many steps the person will walk before taking a step off the bridge. Have the application average 50 trials, and display the average and the greatest number of steps.

thanks for helping...

if i change it to this: `import java.util.*;

public class RandomWalk2 {

public static void main(String[] args) {
    // TODO Auto-generated method stub
    Random rand = new Random();
    double average;
    int greatest=0;
    int moves;
    int total = 0;
    int step;

    step = rand.nextInt((2 - 1) + 1) + 1;

    int location; //location of man on bridge
    for(int i = 0; i < 50; i++)
    {
       moves = 0;
       moves++;
       location = 4;
       total += moves;
       while(true)
       {
          if (step == 2) {
           location++;
          } else {
           location--;
          }

         if((location < 1) || (location > 7)) break;
       }

      if(moves > greatest) {
      greatest = moves;

      }


      }

    average = total / 50;

    System.out.println("The greatest number of steps: " + greatest);
    System.out.println("The average number of steps:  " + average);


    }

}

` then it runs 50 times but the guy only moves 1 stop so my greatest and average always shows as 1.

回答1:

No, it doesn't loop 50 times, because your for loop condition is incorrect. The for loop continues iterating if the condition is true, not false. Change your condition from

for (int i = 0; i == 50; i++) {

to

for (int i = 0; i < 50; i++) {

Then it will run until i < 50 is false (50 times).

回答2:

You need to understand the basics of a for loop.

for (initialization; termination; increment) { statement(s) }

When using this version of the for statement, keep in mind that:

The initialization expression initializes the loop; it's executed once, as the loop begins. When the termination expression evaluates to false, the loop terminates. The increment expression is invoked after each iteration through the loop; it is perfectly acceptable for this expression to increment or decrement a value.

The following link should be helpful:

Java for loops

回答3:

location = 4;
step = rand.nextInt((2 - 1) + 1) + 1;
while (location < 1 || location > 7) {
    ..
}

When will location be less than 1 or greater than 7?

Also the for loop as mentioned by rgettman