Java binary search help

[jato_127]

Ok so I'm in a beginner java class and need help with the errors im getting in this program any help would be great.

 

CODE:

 public class BinSearch{public static final int NOT_FOUND = -1;public static double binarySearch(double[] a, double x){double low=0;double high= a.length-1;double mid;while (low<=high){mid = (low+high)/2;if (a[mid]>x)low = mid+1;if (a[mid]<x)high = mid-1;elsereturn mid;}return NOT_FOUND;} public static void main(String[] args){double SIZE =43.5;double[] a = new double[SIZE];for (double i=0; i<SIZE;i++)a[i] = new Double(i * 2);for (double i=0; i<Size*2; i++)System.out.println("Found"+i+ "at"+binarySearch(a, new Double(i)));}}

 

 

The errors consist with a few Loss of precision and one cannot find symbol

 

Once again thanks for the help.

Edited April 7, 2014 by alpenwasser
added code tags

[auraofjason]

Loss of precision: You can't iterate through a double[] with a double, it must be an int. You can cast a double into an int by doing: (int)double, or (int)mid for your mid double.

 

Cannot find symbol: You set the variable name to be SIZE, but you used Size in your for loop. SIZE and Size are different.

[jato_127]

Ok so i fixed the SIZE issue, thanks, but I'm still confused by the double.  

 

I turned the double mid to int mid and I am still getting errors of loss of precision. specifically at  mid = (low+high)/2, and int SIZE =43.5;.

[fizzlesticks]

Ok so i fixed the SIZE issue, thanks, but I'm still confused by the double.  

 

I turned the double mid to int mid and I am still getting errors of loss of precision. specifically at  mid = (low+high)/2, and int SIZE =43.5;.

int SIZE =43.5 makes no sense because an int can't have decimals. Just drop the .5

The loss of precision is because low and high are still doubles which makes (low+high)/2 a double and you lose precision by going to an int. Either change low and high to ints or cast the result of (low+high)/2 to an int.

[auraofjason]

A double is a floating point number (like 1.1234) while an int is just a whole number (like 1).

 

You can keep mid and SIZE as doubles, but when you iterate with them you can cast them into ints like: (int)mid. So for example in this line instead of: if (a[mid]>x), you can do: if (a[(int)mid]>x).

[Ciccioo]

low, mid and high are all integers, because they're indexes

you're also creating an array of the primitive type 'double', but you fill it with Double objects, i guess it just dacays to primitive type but it's still not necessary

edit

SIZE has to be integer too, because it's a size

[xXxYOLOxSWAGxXx_420BlazeIt]

 

Ok so I'm in a beginner java class and need help with the errors im getting in this program any help would be great.

 

CODE:

 

public class BinSearch

{

public static final int NOT_FOUND = -1;

public static double binarySearch(double[] a, double x)

{

double low=0;

double high= a.length-1;

double mid;

while (low<=high)

{

mid = (low+high)/2;

if (a[mid]>x)

low = mid+1;

if (a[mid]<x)

high = mid-1;

else

return mid;

}

return NOT_FOUND;

}

 

public static void main(String[] args)

{

double SIZE =43.5;

double[] a = new double;

for (double i=0; i<SIZE;i++)

a = new Double(i * 2);

for (double i=0; i<Size*2; i++)

System.out.println("Found"+i+ "at"+binarySearch(a, new Double(i)));

}

}

 

 

The errors consist with a few Loss of precision and one cannot find symbol

 

Once again thanks for the help.

 

 

Use the code tags ffs.

[jato_127]

Thanks for the help guys you explained a lot, I contacted my instructor this morning and he help me figure everything out. once again thanks