Added Interpolation Search and JUnit test.

src/main/java/com/search/InterpolationSearch.java

@@ -0,0 +1,60 @@
+package src.main.java.com.search;
+
+public class InterpolationSearch {
+
+	/**
+	 * A linear interpolation search algorithm that finds the position of a
+	 * target value in an sorted array using its lowest value and highest value.
+	 * 
+	 * Average time-complexity O(log log n) - uniformly distributed.
+	 * Worst-case time-complexity O(n) - non-uniformly distributed
+	 * Worst-case space complexity O(1)
+	 * 
+	 * @param <T>This is any comparable type
+	 * @param arr This is the array where the element should be found
+	 * @param key This is the element to find in the array
+	 * @return The index of the key in the array
+	 */
+	public <T extends Comparable<T>> int findIndex(T arr[], T key) {
+		return checkCondition(arr, key, 0, arr.length - 1);
+	}
+
+	/**
+	 * @param lowIndex The first and smallest element in the sorted array
+	 * @param highIndex The last and largest element in the sorted array
+	 * @return The found key's index in the array through iteration
+	 */
+	private <T extends Comparable<T>> int checkCondition(T arr[], T key, int lowIndex, int highIndex) {
+		boolean conditionOne = lowIndex <= highIndex && key.compareTo(arr[lowIndex]) >= 0;
+		boolean conditionTwo = key.compareTo(arr[lowIndex]) == 0 && key.compareTo(arr[highIndex]) <= 0;
+		while (conditionOne || conditionTwo) {
+			int position = getPostion(arr, key, lowIndex, highIndex);
+			if (arr[position].equals(key))
+				return position;
+
+			if (arr[position].compareTo(key) < 0)
+				lowIndex = position + 1;
+			else
+				highIndex = position - 1;
+		}
+		return -1;
+	}
+
+	/**
+	 * @return The array's current retrieved index position
+	 */
+	private <T> int getPostion(T arr[], T key, int lowIndex, int highIndex) {
+		String startValueString = arr[lowIndex].toString(); //First convert <T> array element to String
+		int startValueInt = Integer.parseInt(startValueString); //Convert String to int to computate later
+		String endValueString = arr[highIndex].toString();
+		int endValueInt = Integer.parseInt(endValueString);
+		String keyValueString = key.toString(); //Repeat for <T> key to later computate
+		int keyValueInt = Integer.parseInt(keyValueString);
+
+		int arrayIndexRangeDiff =  highIndex - lowIndex;
+		int arrayHighLowValuesDiff =  endValueInt - startValueInt;
+		int keyMinusArrayLowValue =  keyValueInt - startValueInt;
+		int position = lowIndex + (((arrayIndexRangeDiff) / (arrayHighLowValuesDiff) * (keyMinusArrayLowValue)));
+		return position;
+	}
+}

src/test/java/com/search/InterpolationSearchTest.java

@@ -0,0 +1,29 @@
+package src.test.java.com.search;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import src.main.java.com.search.InterpolationSearch;
+
+public class InterpolationSearchTest {
+
+	@Test
+	public void testInterpolationSearch() {
+		InterpolationSearch interpolationSearch = new InterpolationSearch();
+		
+		Integer arr[] = {10, 12, 13, 16, 18, 19, 21};
+		int x = 18;
+		int index = interpolationSearch.findIndex(arr, x);
+		Assert.assertEquals("Incorrect index", 4, index);
+
+		Integer arrTwo[] = {-210, -190, -180, -160, -130, -120, -100};
+		x = -190;
+		index = interpolationSearch.findIndex(arrTwo, x);
+		Assert.assertEquals("Incorrect index", 1, index);
+		
+		String arrString[] = {"10", "12", "13", "16", "22", "25","29"};
+		String stringX = "13";
+		index = interpolationSearch.findIndex(arrString, stringX);
+		Assert.assertEquals("Incorrect index", 2, index);
+	}
+}