Elements of Programming Interviews (in Java)

public static short countBits(int x) {
            short numBits = 0;
            while (x != 0) {
                    numBits += (x & 1);
                    x >>>= 1;
            }
            return numBits;
}
public static void main(String[] args) {
        System.out.println(countBits(15));
}

public static void main(String[] args) {
    System.out.println(6&4);
    System.out.println(1|2);
    System.out.println(8>>1);
    System.out.println(-16>>>2);
    System.out.println(1<<10);
    System.out.println(~0);
}

public static void main(String[] args) {
    System.out.println(Integer.MIN_VALUE);
    System.out.println(Float.MAX_VALUE);
    System.out.println(Double.SIZE);
    System.out.println(Boolean.TRUE);
}

public static void main(String[] args) {
    System.out.println(Double.valueOf("1.23"));
    System.out.println(Boolean.valueOf(true));
    System.out.println(Integer.parseInt("42"));
    System.out.println(Float.toString(-1.23F));
}

import static java.lang.Math.*;
public static void main(String[] args) {
    System.out.println(abs(-34.5));
    System.out.println(ceil(2.17));
    System.out.println(floor(-34.5));
    System.out.println(min(-3,4.5));
    System.out.println(max(-3,4.5));
    System.out.println(pow(2.71,3.14));
    System.out.println(sqrt(225));
}

public static void main(String[] args) {
    char x = '6';
    System.out.println(Character.getNumericValue(x));
    System.out.println(x - '0');
    System.out.println(String.valueOf(123));
}