Empty strings

Question

How can i effectively detect for empty strings, i'va tried "if (someString.length()==0) ... " and the expression "(someString=="")".
who can explain????
gr. Razorblade

Answer 1

I agree with levi_h,. It's a common mistake to compare a string object with a known (static) string in the wors of orders (s.equals("mystring") vs "mystring".equals(s))... The last one is safe, it will never throw a NullPointerException if s is null.
I usually implement a method in a utility class that looks like this.
public static final String isNullOrEmpty(final String s) {
  return s == null || s.length() == 0;
}Regards,
  //Håkan
PS. Checking the length of a string is much faster than comparing it with an empty string...
public class sequals {
  public static final long start() {
    return System.currentTimeMillis();
  public static final long stop(final long l) {
    return start() - l;
  public static final boolean test1(final String s) {
    return s.equals("");
  public static final void test1(final String s, final int n) {
    for (int i = 0; i < n; ++i) {
      test1(s);
  public static final boolean test2(final String s) {
    return s.length() == 0;
  public static final void test2(final String s, final int n) {
    for (int i = 0; i < n; ++i) {
      test2(s);
  public static final void main(final String[] args) {
    final int times = 1000000;
    long n1    = start();
    test1("Am I empty?", times);
    n1 = stop(n1);
    long n2    = start();
    test2("Am I empty?", times);
    n2 = stop(n2);
    System.out.println("Test1: " + n1 + " ms.");
    System.out.println("Test2: " + n2 + " ms.");
}