Summary of methods for Java to determine whether a string is empty

Here are four ways that Java determines whether a string is empty:

Method One: Most people use a method that is intuitive, convenient, but inefficient:

if (s = = NULL | | "". Equals (s));
Method Two: Compare string length, high efficiency, is the best I know of a method:

if (s = = NULL | | s.length () <= 0);
Method Three: Java SE 6.0 only begins to provide methods that are nearly equal in efficiency and method two, but for compatibility reasons it is recommended to use method two.

if (s = = NULL | | s.isempty ());

Method Four: This is a more intuitive, simple method, and the efficiency is very high, and the efficiency of method two or three is similar:

if (s = = NULL | | s = = "");

Note: s = = null is necessary to exist.

If the String type is null, the Go to equals (string) or length () will throw java.lang.NullPointerException.

and the order of S==null must appear in front, otherwise it will also throw java.lang.NullPointerException.

The following Java code:

String str = NULL;

if (Str.equals ("") | | Str= = = null) {//throws an exception

SYSTEM.OUT.PRINTLN ("Success");

}

". Equals (str); the rear ensures that no null error is encountered.