JavaAlgorithms/strings/CharactersSame.java

package strings;

public class CharactersSame {

  /** Driver Code */
  public static void main(String[] args) {
    assert isAllCharactersSame("");
    assert !isAllCharactersSame("aab");
    assert isAllCharactersSame("aaa");
    assert isAllCharactersSame("11111");
  }

  /**
   * check if all the characters of a string are same
   *
   * @param s the string to check
   * @return {@code true} if all characters of a string are same, otherwise {@code false}
   */
  public static boolean isAllCharactersSame(String s) {
    for (int i = 1, length = s.length(); i < length; ++i) {
      if (s.charAt(i) != s.charAt(0)) {
        return false;
      }
    }
    return true;
  }
}