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Very simple code for number search gives me infinite loop

开发者 https://www.devze.com 2022-12-31 01:13 出处:网络
I am a newbie Computer Science high school student and I have trouble with a small snippet of code. Basically, my code should perform a basic CLI search in an array of integers. However, what happens

I am a newbie Computer Science high school student and I have trouble with a small snippet of code. Basically, my code should perform a basic CLI search in an array of integers. However, what happens is I get what appears to be an infinite loop (BlueJ, the compiler I'm using, gets stuck and I have to reset the machine). I have set break points but I still don't quite get the problem...(I don't even understand most of the things that it tells me)

Here's the offending code (assume that "ArrayUtil" works, because it does):

import java.util.Scanner;
public class intSearch
{
   public static void main(String[] args)
   {
       search();
   }

   public static void search()
   {
       i开发者_JAVA百科nt[] randomArray = ArrayUtil.randomIntArray(20, 100);
       Scanner searchInput = new Scanner(System.in);
       int searchInt = searchInput.nextInt();
       if (findNumber(randomArray, searchInt) == -1)
       {
           System.out.println("Error");
       }else System.out.println("Searched Number: " + findNumber(randomArray, searchInt));
   }

   private static int findNumber(int[] searchedArray, int searchTerm)
   {
      for (int i = 0; searchedArray[i] == searchTerm && i < searchedArray.length; i++)
      {
          return i;
      }
      return -1;
   }
}

This has been bugging me for some time now...please help me identify the problem!


I don't know about the infinite loop but the following code is not going to work as you intended. The i++ can never be reached so i will always have the value 0.

for (int i = 0; searchedArray[i] == searchTerm && i < searchedArray.length; i++)
{
    return i;
}
return -1;

You probably mean this:

for (int i = 0; i < searchedArray.length; i++)
{
    if (searchedArray[i] == searchTerm)
    {
        return i;
    }
}
return -1;


I don't know what is the class ArrayUtil (I can not import is using my Netbeans). When I try to change that line with the line int[] randomArray = {1 , 2, 3, 5, 7, 10, 1 , 5}; It works perfectly.

And you should change the loop condition. I will not tell you why but try with my array and you will see the bug soon. After you see it, you can fix it:)


There are 4 basic issues here.
1. Putting searchedArray[i] == searchTerm before i < searchedArray.length can result in an out-of-bounds exception. You must always prevent that kind of code.
2. Your intention seems to be the opposite of your code. Your method name implies finding a search term. But, your code implies that you want to continue your loop scan until the search term is not found, although your loop won't do that either. Think of "for (; this ;) { that } " as "while this do that".
3. Place a break point at the beginning of "search". Then, with a small array, step through the code line by line with the debugger and watch the variables. They don't lie. They will tell you exactly what's happening.
4. Please use a standard IDE and compiler, such as Eclipse and Sun's JDK 6 or 7. Eclipse with JDK 7 is a serious combination that doesn't exhibit a strange "infinite loop" as you describe above.

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