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Task/Benfords-law/Java/benfords-law.java

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+import java.math.BigInteger;
+
+public class Benford {
+    private static interface NumberGenerator {
+        BigInteger[] getNumbers();
+    }
+
+    private static class FibonacciGenerator implements NumberGenerator {
+        public BigInteger[] getNumbers() {
+            final BigInteger[] fib = new BigInteger[ 1000 ];
+            fib[ 0 ] = fib[ 1 ] = BigInteger.ONE;
+            for ( int i = 2; i < fib.length; i++ )
+                fib[ i ] = fib[ i - 2 ].add( fib[ i - 1 ] );
+            return fib;
+        }
+    }
+
+    private final int[] firstDigits = new int[ 9 ];
+    private final int   count;
+
+    private Benford( final NumberGenerator ng ) {
+        final BigInteger[] numbers = ng.getNumbers();
+        count = numbers.length;
+        for ( final BigInteger number : numbers )
+            firstDigits[ Integer.valueOf( number.toString().substring( 0, 1 ) ) - 1 ]++;
+    }
+
+    public String toString() {
+        final StringBuilder result = new StringBuilder();
+        for ( int i = 0; i < firstDigits.length; i++ )
+            result.append( i + 1 )
+                .append( '\t' ).append( firstDigits[ i ] / ( double )count )
+                .append( '\t' ).append( Math.log10( 1 + 1d / ( i + 1 ) ) )
+                .append( '\n' );
+        return result.toString();
+    }
+
+    public static void main( final String[] args ) {
+        System.out.println( new Benford( new FibonacciGenerator() ) );
+    }
+}