Added number to word converter

src/zutil/converters/NumberToWordsConverter.java

@@ -0,0 +1,92 @@
+package zutil.converters;
+
+import java.util.HashMap;
+
+public class NumberToWordsConverter {
+	
+	private static final String ZERO_STRINGS = "zero";
+	// Indexes to lookup
+	private static final int[] NUMERIC_INDEXES = new int[]{
+		9,/*1000 000 000*/
+		6,/*1000 000*/
+		3,/*1000*/
+		2 /*100*/};
+	private static final HashMap<Long, String> NUMERIC_STRINGS;
+	static{
+		NUMERIC_STRINGS = new HashMap<>();
+		NUMERIC_STRINGS.put(1l, "one");
+		NUMERIC_STRINGS.put(2l, "two");
+		NUMERIC_STRINGS.put(3l, "three");
+		NUMERIC_STRINGS.put(4l, "four");
+		NUMERIC_STRINGS.put(5l, "five");
+		NUMERIC_STRINGS.put(6l, "six");
+		NUMERIC_STRINGS.put(7l, "seven");
+		NUMERIC_STRINGS.put(8l, "eight");
+		NUMERIC_STRINGS.put(9l, "nine");
+		NUMERIC_STRINGS.put(10l, "ten");
+		NUMERIC_STRINGS.put(11l, "eleven");
+		NUMERIC_STRINGS.put(12l, "twelve");
+		NUMERIC_STRINGS.put(13l, "thirteen");
+		NUMERIC_STRINGS.put(14l, "fourteen");
+		NUMERIC_STRINGS.put(15l, "fifteen");
+		NUMERIC_STRINGS.put(16l, "sixteen");
+		NUMERIC_STRINGS.put(17l, "seventeen");
+		NUMERIC_STRINGS.put(18l, "eightteen");
+		NUMERIC_STRINGS.put(19l, "nineteen");
+		
+		NUMERIC_STRINGS.put(20l, "twenty");
+		NUMERIC_STRINGS.put(30l, "thirty");
+		NUMERIC_STRINGS.put(40l, "forty");
+		NUMERIC_STRINGS.put(50l, "fifty");
+		NUMERIC_STRINGS.put(60l, "sixty");
+		NUMERIC_STRINGS.put(70l, "seventy");
+		NUMERIC_STRINGS.put(80l, "eighty");
+		NUMERIC_STRINGS.put(90l, "ninety");
+		
+		NUMERIC_STRINGS.put(100l, "hundred");
+		NUMERIC_STRINGS.put(1_000l, "thousand");
+		NUMERIC_STRINGS.put(1000_000l, "million");
+		NUMERIC_STRINGS.put(1000_000_000l, "billion");
+	}
+	
+	
+	/**
+	 * Given an integer in the range -20 to 20 will return a String with
+	 * that number converted to words. For example, an input of 15 results in 
+	 * an output of "fifteen". An input of -4 returns "minus four".
+	 * 
+	 * @param	 num	a number to be converted to words.
+	 * @return the number as words.
+	 */
+	public String convert(int num) {
+		if (num == 0)
+			return ZERO_STRINGS;
+		
+		long tmpNum = num;
+		StringBuilder buffer = new StringBuilder();
+		if (tmpNum < 0){ // Negative number
+			tmpNum *= -1;
+			buffer.append("minus ");
+		}
+		
+		for(int i : NUMERIC_INDEXES){
+			long pow = (int)Math.pow(10, i);
+			if (tmpNum >= pow){
+				long numberAtIndex = tmpNum/pow; // The number at position 3
+				tmpNum -= numberAtIndex*pow;
+				buffer.append( convert((int)numberAtIndex) ).append(" ");
+				buffer.append( NUMERIC_STRINGS.get( pow ) ).append(" ");
+			}
+		}
+		if (tmpNum >= 20){ // second number in the integer
+			long numberAtIndex = ((tmpNum % 100)/10)*10; // The number at position 2
+			tmpNum -= numberAtIndex;
+			buffer.append( NUMERIC_STRINGS.get(numberAtIndex) ).append(" ");
+		}
+		if (NUMERIC_STRINGS.containsKey(tmpNum))
+			buffer.append(NUMERIC_STRINGS.get(tmpNum));
+		return buffer.toString().trim();
+	}
+
+
+}

test/zutil/test/NumberToWordsConverterTest.java

@@ -0,0 +1,72 @@
+package zutil.test;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.CoreMatchers.is;
+import static org.junit.Assert.assertThat;
+
+import java.util.Arrays;
+import java.util.Collection;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+import org.junit.runners.Parameterized.Parameters;
+import zutil.converters.NumberToWordsConverter;
+
+
+@RunWith(Parameterized.class)
+public class NumberToWordsConverterTest {
+		
+	@Parameters
+	public static Collection<Object[]> parameters() {		
+		Object[][] data = new Object[][] {
+			{-77,  "minus seventy seven"}
+			, {-2, "minus two"}
+			, {1,  "one"}
+			, {0,  "zero"}
+			, {7,  "seven"}
+			, {11, "eleven"}
+			, {12, "twelve"}
+			, {17, "seventeen"}
+			, {20, "twenty"}
+			, {21, "twenty one"}
+			, {23, "twenty three"}
+			, {25, "twenty five"}
+			, {30, "thirty"}
+			, {34, "thirty four"}
+			, {50, "fifty"}
+			, {70, "seventy"}
+			, {100, "one hundred"}
+			, {110, "one hundred ten"}
+			, {131, "one hundred thirty one"}
+			, {222, "two hundred twenty two"}
+			, {1000, "one thousand"}
+			, {10_000, "ten thousand"}
+			, {100_000, "one hundred thousand"}
+			, {1000_000, "one million"}
+			, {10_000_000, "ten million"}
+			, {Integer.MAX_VALUE, "two billion one hundred forty seven million four hundred eighty three thousand six hundred forty seven"}
+			, {Integer.MIN_VALUE, "minus two billion one hundred forty seven million four hundred eighty three thousand six hundred forty eight"}
+			};
+		return Arrays.asList(data);
+	}
+	
+	
+	private int input;
+	private String expected;
+	
+
+	public NumberToWordsConverterTest(int input, String expected) {
+		this.input = input;
+		this.expected = expected;
+	}
+
+	@Test
+	public void testConvert() {
+		assertThat(new NumberToWordsConverter().convert(input)
+													, is(equalTo(expected)));
+	}
+
+}
+	
+