Get english string representation of given number

.classpath

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+<?xml version="1.0" encoding="UTF-8"?>
+<classpath>
+	<classpathentry kind="src" output="target/classes" path="src/main/java">
+		<attributes>
+			<attribute name="optional" value="true"/>
+			<attribute name="maven.pomderived" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry excluding="**" kind="src" output="target/classes" path="src/main/resources">
+		<attributes>
+			<attribute name="maven.pomderived" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="src" output="target/test-classes" path="src/test/java">
+		<attributes>
+			<attribute name="optional" value="true"/>
+			<attribute name="maven.pomderived" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry excluding="**" kind="src" output="target/test-classes" path="src/test/resources">
+		<attributes>
+			<attribute name="maven.pomderived" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/J2SE-1.5">
+		<attributes>
+			<attribute name="maven.pomderived" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="con" path="org.eclipse.m2e.MAVEN2_CLASSPATH_CONTAINER">
+		<attributes>
+			<attribute name="maven.pomderived" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="output" path="target/classes"/>
+</classpath>

.project

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+<?xml version="1.0" encoding="UTF-8"?>
+<projectDescription>
+	<name>integerToStringConvertor</name>
+	<comment></comment>
+	<projects>
+	</projects>
+	<buildSpec>
+		<buildCommand>
+			<name>org.eclipse.jdt.core.javabuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+		<buildCommand>
+			<name>org.eclipse.m2e.core.maven2Builder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+	</buildSpec>
+	<natures>
+		<nature>org.eclipse.jdt.core.javanature</nature>
+		<nature>org.eclipse.m2e.core.maven2Nature</nature>
+	</natures>
+</projectDescription>

.settings/org.eclipse.jdt.core.prefs

@@ -0,0 +1,5 @@
+eclipse.preferences.version=1
+org.eclipse.jdt.core.compiler.codegen.targetPlatform=1.5
+org.eclipse.jdt.core.compiler.compliance=1.5
+org.eclipse.jdt.core.compiler.problem.forbiddenReference=warning
+org.eclipse.jdt.core.compiler.source=1.5

.settings/org.eclipse.m2e.core.prefs

@@ -0,0 +1,4 @@
+activeProfiles=
+eclipse.preferences.version=1
+resolveWorkspaceProjects=true
+version=1

pom.xml

@@ -0,0 +1,8 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+  <groupId>com.dcubelic</groupId>
+  <artifactId>integerToStringConvertor</artifactId>
+  <version>0.0.1-SNAPSHOT</version>
+  <description>Integer to String convertor</description>
+
+</project>

src/main/java/integerToStringConvertor/NumberUtility.java

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+package integerToStringConvertor;
+
+/**
+ * Utility class used to convert integer (or long) numbers to their English representations.
+ * @author Dominik Čubelić
+ *
+ */
+public class NumberUtility {
+
+	private static String[] DIGITS = {"zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"};
+	private static String[] TEN_THROUGH_NINETEEN = {"ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen",
+			"sixteen", "seventeen", "eighteen", "nineteen"};
+	private static String[] TENS = {"", "ten", "twenty", "thirty", "fourty", "fifty", "sixty", "seventy", "eighty", "ninety"};
+	private static String[] VALUES = {"", "thousand", "million", "billion", "trillion", "quadrillion", "quintillion", "sextillion"};
+
+	private static String MINUS = "minus";
+	private static String HUNDRED = "hundred";
+	private static String ZERO = "zero";
+	private static String AND = "and";
+
+	/**
+	 * Returns English string representation for a given number.
+	 * @param number
+	 * @return English string representation of given number.
+	 */
+	public static String getStringRepresentation(long number) {
+		StringBuilder sb = new StringBuilder();
+
+		boolean negative = number < 0;
+		number = Math.abs(number);
+
+		int br = 0;
+		while(number > 0) {
+			String tripleDigits = convertTripleDigits((int) (number%1000));
+			String str = tripleDigits.equals(ZERO) ? "" : tripleDigits + " " + VALUES[br] + " ";
+			number/=1000;
+			br++;
+			sb.insert(0, str);
+		}
+
+		if(negative) {
+			sb.insert(0, MINUS + " ");
+		}
+
+		return sb.toString().trim();
+	}
+
+	private static String convertSingleDigit(int digit) {
+		if(digit < 0 || digit > 9) {
+			throw new IllegalArgumentException("Invalid digit.");
+		}
+
+		return DIGITS[digit];
+	}
+
+	private static String convertDoubleDigits(int digits) {
+		if(digits < 0 || digits > 99) {
+			throw new IllegalArgumentException("Invalid digits");
+		}
+
+		if(digits < 10) return convertSingleDigit(digits);
+		else if (digits < 20) return TEN_THROUGH_NINETEEN[digits-10];
+
+		String tens = TENS[digits/10];
+		String digit = DIGITS[digits%10];
+
+		return tens + (digit.equals(ZERO) ? "" : " " + digit);
+	}
+
+	private static String convertTripleDigits(int digits) {
+		if(digits < 0 || digits > 999) {
+			throw new IllegalArgumentException("Invalid digits.");
+		}
+
+		if(digits < 100) return convertDoubleDigits(digits);
+
+		String firstDigitString = convertSingleDigit(digits/100);
+		int tens = digits%100;
+
+		String hundredsString = firstDigitString.equals(ZERO) ? "" : firstDigitString + " " + HUNDRED;
+		String tensString = convertDoubleDigits(tens);
+
+		return hundredsString + (tensString.equals(ZERO) ? "" : " " + AND + " " + tensString);
+ 	}
+
+}