refactor code

Author: freemanzhang

src/facebook/hard/IntegerToEnglishWords.java

@@ -1,64 +1,73 @@
-package facebook.hard;
-
-/**
- * Convert a non-negative integer to its english words representation. Given input is guaranteed to be less than 231 - 1.
-
-For example,
-123 -> "One Hundred Twenty Three"
-12345 -> "Twelve Thousand Three Hundred Forty Five"
-1234567 -> "One Million Two Hundred Thirty Four Thousand Five Hundred Sixty Seven"
- */
-
-public class IntegerToEnglishWords
-{
-    public String numberToWords( int num )
-    {
-        String[] bigs = new String[]{ " Thousand", " Million", " Billion" };
-        StringBuilder result = new StringBuilder();
-        int i = 0;
-        result.append( convertToWords( num % 1000 ) + bigs[i] );
-        num /= 1000;
-        
-        while ( num > 0 )
-        {
-        	if ( num % 1000 != 0 )
-        	{
-        		result.insert( 0, convertToWords( num % 1000 ) + bigs[i] );
-        	}
-        	i++;
-        	num /= 1000;
-        }
-        return result.length() == 0 ? "Zero" : result.toString().trim();
-    }
-    
-    public String convertToWords( int num )
-    {
-        String[] digit = {"", " One", " Two", " Three", " Four", " Five",
-                " Six", " Seven", " Eight", " Nine"};
-        String[] tenDigit = {" Ten", " Eleven", " Twelve", " Thirteen", " Fourteen", " Fifteen",
-                " Sixteen", " Seventeen", " Eighteen", " Nineteen"};
-        String[] tenMutipleDigit = {"", "", " Twenty", " Thirty", " Forty", " Fifty",
-                " Sixty", " Seventy", " Eighty", " Ninety"};
-        StringBuilder sb = new StringBuilder();
-        if ( num >= 100 )
-        {
-            sb.append( digit[num / 100] ).append(" Hundred");
-            num %= 100;
-        }
-        if ( num > 9 && num < 20 )
-        {
-            sb.append( tenDigit[num - 10] );
-        } 
-        else 
-        {
-            if ( num >= 20 )
-            {
-                sb.append( tenMutipleDigit[num / 10] );
-                num %= 10;
-            }
-            sb.append( digit[num] );
-        }
-        return sb.toString();
-    }
-
-}
+package facebook.hard;
+
+import org.junit.Test;
+
+/**
+ * Convert a non-negative integer to its english words representation. Given input is guaranteed to be less than 231 - 1.
+
+For example,
+123 -> "One Hundred Twenty Three"
+12 345 -> "Twelve Thousand Three Hundred Forty Five"
+1 234 567 -> "One Million Two Hundred Thirty Four Thousand Five Hundred Sixty Seven"
+ */
+
+public class IntegerToEnglishWords
+{
+    public String numberToWords( int num )
+    {
+        String[] bigs = new String[]{ "", " Thousand", " Million", " Billion" };
+        StringBuilder result = new StringBuilder();
+
+        for ( int i = 0; num > 0; i++, num /= 1000 )
+        {
+        	if ( num % 1000 != 0 )
+        	{
+        		result.insert( 0, convertToWords( num % 1000 ) + bigs[i] );
+        	}
+        }
+
+        return result.length() == 0 ? "Zero" : result.toString().trim();
+    }
+    
+    private String convertToWords( int num )
+    {
+        String[] singleDigit = { "", " One", " Two", " Three", " Four", " Five",
+                " Six", " Seven", " Eight", " Nine" };
+        String[] tenDigit = { " Ten", " Eleven", " Twelve", " Thirteen", " Fourteen", " Fifteen",
+                " Sixteen", " Seventeen", " Eighteen", " Nineteen" };
+        String[] biggerThanTwenty = { "", "", " Twenty", " Thirty", " Forty", " Fifty",
+                " Sixty", " Seventy", " Eighty", " Ninety" };
+        
+        StringBuilder sb = new StringBuilder();
+        if ( num >= 100 )
+        {
+            sb.append( singleDigit[num / 100] ).append(" Hundred");
+            num %= 100;
+        }
+
+        if ( num >= 20 )
+        {
+            sb.append( biggerThanTwenty[num / 10] );
+            num %= 10;
+            sb.append( singleDigit[num] );
+        }
+        else if ( num > 9 && num < 20 )
+        {
+            sb.append( tenDigit[num - 10] );
+        } 
+        else
+        {
+            sb.append( singleDigit[num] );        	
+        }
+        
+        return sb.toString();
+    }
+
+    @Test
+    public void test()
+    {
+    	System.out.println( numberToWords( 1234567 ) );
+    	System.out.println( numberToWords( 12345 ) );
+    	System.out.println( numberToWords( 123 ) );
+    }
+}