- Example 1: Write a function to reverse a string.
// Question #1
public static String reverse(final String s) {
final char[] chars = s.toCharArray();
final int pivot = chars.length / 2;
for (int i = 0; i < pivot; i++) {
final int pos = chars.length - i - 1;
final char c = chars[i];
final char d = chars[pos];
chars[i] = d;
chars[pos] = c;
}
return String.valueOf(chars);
}
- Example 2: Write function to compute Nth fibonacci number:
public static int fibonacci(final int n) {
return n <= 1 ? n : fibonacci(n - 1) + fibonacci(n - 2);
}
- Example 3: Print out the grade-school multiplication table up to 12x12
public static void printMultiplicationTable(final int n) {
for (int i = 1; i <= n; i++) {
for (int k = 1; k <= n; k++) {
System.out.print(String.format("%4d ", k * i));
}
System.out.println();
}
}
- Example 4: Write a function that sums up integers from a text file, one int per line.
public static int sumFile(final String path) throws FileNotFoundException {
final File file = new File(path);
final Scanner scanner = new Scanner(file);
int sum = 0;
while (scanner.hasNext()) {
sum += Integer.parseInt(scanner.nextLine());
}
scanner.close();
return sum;
}
- Example 5: Write function to print the odd numbers from 1 to 99.
public static void printOdds(final int max) {
for (int i = 1; i <= max; i += 2) {
System.out.print(i + " ");
}
}
- Example 6: Find the largest int value in an int array.
public static int max(final int[] ints) {
int max = ints[0];
for (int i = 1; i < ints.length; i++) {
if (max < ints[i]) {
max = ints[i];
}
}
return max;
}
- Example 7: Format an RGB value (three 1-byte numbers) as a 6-digit hexadecimal string.
public static String rgbToHex(final int r, final int g, final int b) {
return (toHex(r) + toHex(g) + toHex(b)).toUpperCase();
}
private static String toHex(final int i) {
final String s = Integer.toHexString(i);
return s.length() == 1 ? "0" + s : s;
}