Ahmed Hashim's Blog

Compare String to a literal.. coding style

I saw many times code written by geeks, comparing String to literals in this style

public boolean compareUser(String name)
{
if("Ahmed Hashim".equals(name))
{
//do staff here
return true;
}
return false;
}

public boolean compareUser(String name)
{
if(name.equals("Ahmed Hashim"))
{
//do staff here
return true;
}
return false;
}

compareUser(null);

I think you got it, passing null will not need check in the first version because you are not accessing the “.equals” method inside the passed object, while the 2nd version will cause NullPointerException!

Mirror:
http://egjug.org/hashimblog/2007/03/08/compare-string-to-a-literal-coding-style/

Comments

• Surely the the first is the normal code style? The second is unsafe so the former is always going to better unless you actually want an NPE thrown.

  Writing safe code is not solely in the domain of geeks.

  Posted by: goron on March 10, 2007 at 05:14 AM

• I agree. The first approach is the normal coding approach. Second is simply bad programming that can lead to errors.

  Posted by: hanuska on March 12, 2007 at 02:17 AM

• Hi goron, yes, I think the first one is more safe than the second.

  sure hanuska.

  Posted by: ahashim on March 12, 2007 at 02:40 AM

• I'd say the second one was "normal". The first one is certainly more "safe", however, it's disadvantage is (1) it doesn't read very well, especially with more complicated expressions, and (2) it may cause a subtle bug to go comepletely unnoticed.

  Ideally, you would want to do something like this:

  public boolean compareUser(String name) {
  if (name == null) throw new IllegalArgumentException("Name should be specified");
  return name.equals("Ahmed Hashim");
  }

  
  This way (1) it doesn't matter which way you do it, and (2) you are guarding against null values, which you should try not to use as much as possible, see NullObject pattern.

  Posted by: fiath on March 12, 2007 at 06:06 AM

• The example is just good-style (or normal-style) Java

  Btw, in similar way you may find the following from people with serious C/C++ background:

  int x = ...;
  if (0 == x) {
  ...
  }
  or
  if ( someFunc() == x) {
  ...
  }

  
  Guess why variable is on right side of comparison ;)

  VS
  

  Posted by: vsilaev on March 12, 2007 at 09:30 AM

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