Find closest value in an ordered list

Question

I am wondering how you would write a simple java method finding the closest Integer to a given value in a sorted Integer list.

Here is my first attempt:

public class Closest {      private static List<Integer> integers = new ArrayList<Integer>();      static {         for (int i = 0; i <= 10; i++) {             integers.add(Integer.valueOf(i * 10));         }     }      public static void main(String[] args) {          Integer closest = null;         Integer arg = Integer.valueOf(args[0]);          int index = Collections.binarySearch(                 integers, arg);          if (index < 0) /*arg doesn't exist in integers*/ {             index = -index - 1;             if (index == integers.size()) {                 closest = integers.get(index - 1);             } else if (index == 0) {                 closest = integers.get(0);             } else {                 int previousDate = integers.get(index - 1);                 int nextDate =  integers.get(index);                 if (arg - previousDate < nextDate - arg) {                     closest = previousDate;                 } else {                     closest = nextDate;                 }             }         } else /*arg exists in integers*/ {             closest = integers.get(index);         }         System.out.println("The closest Integer to " + arg + " in " + integers                 + " is " + closest);     } } 

What do you think about this solution ? I am sure there is a cleaner way to do this job.

Maybe such method exists somewhere in the Java libraries and I missed it ?

Answer 1

try this little method:

public int closest(int of, List<Integer> in) {     int min = Integer.MAX_VALUE;     int closest = of;      for (int v : in) {         final int diff = Math.abs(v - of);          if (diff < min) {             min = diff;             closest = v;         }     }      return closest; } 

some testcases:

private final static List<Integer> list = Arrays.asList(10, 20, 30, 40, 50);  @Test public void closestOf21() {     assertThat(closest(21, list), is(20)); }  @Test public void closestOf19() {     assertThat(closest(19, list), is(20)); }  @Test public void closestOf20() {     assertThat(closest(20, list), is(20)); }