String concatinations
Even thouhg
Java comes with the "+" (plus operator) overloaded for Strings only to make it more convinient for developers to use, this convinience feature comes with hidden cost. Strings are immutable. It means that every time we write:
String a = "string a";
String b = "string b";
String c = a + b;
it will create 3
Java objects. This does not seem like a big problem. Now try to imagine some log messages that are composed from different Strings:
System.out.println( "user account:"
+ userAccount.id
+ " is emabled since:"
+ userAccount.activationDate")
and if this portion of the code is executed by councurent threads under havy load it might quickly become a botleneck.
Comparing a String object to a contant with equals
There are two ways of comparing a string object with the string constant.
The first way is straigh forward and the most obvious:
String myString = "genericString";
if(myString.equals("genericString")) {
System.out.println("great");
}The same thing can be accomplished better with following code:
String myString = "genericString";
if("genericString".equals(myString)) {
System.out.println("great");
}Since "genericString" is a Java Object, the
java.lang.Object methods can be called directly on it.
It's better because it's more readable and more error prone. If for some reason
myString object is
null the first example will throw a
NullPointerException wich will have to be handled. The second example will just return
false.
http://pingability.com
