问题:

Possible Duplicate:
Comparing StringBuffer content with equals

StringBuffer s1= new StringBuffer("Test");
StringBuffer s2 = new StringBuffer("Test");
if(s1.equals(s2)) {
  System.out.println("True");
} else {
  System.out.println("False");
}

Why does that code print "False"?

回答1:

StringBuffer does not override the Object.equals method, so it is not performing a string comparison. Instead it is performing a direct object comparison. Your conditional may as well be if(s1==s2). If you want to compare the strings you'll need to turn the buffers into strings first.

See http://java.sun.com/j2se/1.5.0/docs/api/java/lang/StringBuffer.html

Edit: I'm assuming we're in a java world.

p.s. If you're in a single-threaded environment, or your buffers are isolated to a single thread, you should really be using a StringBuilder instead of a StringBuffer.

回答2:

StringBuffer equals isn't overridden to check content. It's using the default "shallow equals" that compares references it inherits from java.lang.Object.