Coding Samples

Write a function to reverse a string.

public static String reverse ( String s ) { int length = s.length(), last = length − 1; char[] chars = s.toCharArray(); for ( int i = 0; i < length/2; i++ ) { char c = chars[i]; chars[i] = chars[last − i]; chars[last − i] = c; } return new String(chars); }

Example output for "Madam, I'm Adam": madA m'I ,madaM

Write function to compute Nth fibonacci number:

 static long fib(int n) { return n <= 1 ? n : fib(n-1) + fib(n-2); }

 public static void main ( String[] args ) { for ( int i = 0; i < 10; i++ ) { System.out.print ( fib(i) + ", " ); } System.out.println ( fib(10) ); }

Test harness output: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55

Print out the grade-school multiplication table up to 12x12

 public static void multTables ( int max ) { for ( int i = 1; i <= max; i++ ) { for ( int j = 1; j <= max; j++ ) { System.out.print ( String.format ( "%4d", j * i )); } System.out.println(); } }

Example output:

   1   2   3   4   5   6   7   8   9  10  11  12
   2   4   6   8  10  12  14  16  18  20  22  24
   3   6   9  12  15  18  21  24  27  30  33  36
   4   8  12  16  20  24  28  32  36  40  44  48
   5  10  15  20  25  30  35  40  45  50  55  60
   6  12  18  24  30  36  42  48  54  60  66  72
   7  14  21  28  35  42  49  56  63  70  77  84
   8  16  24  32  40  48  56  64  72  80  88  96
   9  18  27  36  45  54  63  72  81  90  99 108
  10  20  30  40  50  60  70  80  90 100 110 120
  11  22  33  44  55  66  77  88  99 110 121 132
  12  24  36  48  60  72  84  96 108 120 132 144

Write a function that sums up integers from a text file, one int per line.

 public static void sumFile ( String name ) { try { int total = 0; BufferedReader in = new BufferedReader ( new FileReader ( name )); for ( String s = in.readLine(); s != null; s = in.readLine() ) { total += Integer.parseInt ( s ); } System.out.println ( total ); in.close(); } catch ( Exception xc ) { xc.printStackTrace(); } }

Write function to print the odd numbers from 1 to 99.

 public static void printOdds() { for (int i = 1; i < 100; i += 2) { System.out.println ( i ); } }

Find the largest int value in an int array.

 public static int largest ( int[] input ) { int max = Integer.MIN_VALUE; for ( int i = 0; i < input.length; i++ ) { if ( input[i] > max ) max = input[i]; } return max; }

Format an RGB value (three 1-byte numbers) as a 6-digit hexadecimal string.

 public String formatRGB ( int r, int g, int b ) { return (toHex(r) + toHex(g) + toHex(b)).toUpperCase(); } public String toHex ( int c ) { String s = Integer.toHexString ( c ); return ( s.length() == 1 ) ? "0" + s : s; }

File I/O

 public static void main(String args[]) throws Exception { FileReader fr = new FileReader("FileReaderDemo.java"); BufferedReader br = new BufferedReader(fr); String s; while((s = br.readLine()) != null) { System.out.println(s); } fr.close(); }

Leave a Reply Cancel reply