what is "isDefined" function in java?

[GoSooJJ]

hi all~
I'm new to java.
currently i have a project that convert php to jsp. php has "isset(variable name)" function for look for variable that already defined or not. how does jsp works? I tried to find this simple function, but no luck.
Please help me out.

Thank you~
JJ //

 

[wushutwist]

Need further clarification but I will give you the first thing I could think of.

You can always check if a variable is null to determine if it has been "set". Example:
Object x = null;
...
if (x == null) {
/* not set yet */
}
else {
/* x is set */
} Wushutwist

 

[GoSooJJ]

thx Wushutwist,

ok here is what i need.
in php, we can have 'isset()' function to see the variable is defined or not. something like this.

if (isset(varName) AND varName == "DefinedVariable&quot
echo ("hello"

therefore even without initialize variable name 'varName' we can check for the either it's defined or not. if i run this code in jsp

if (varName == NULL)
...do something...

above code will generate error that 'varName' is not defined. i want to know that is there any way that i can check the variable already initialized or not...

thx again,
JJ //

 

[wushutwist]

No. You must define a variable before you use it in almost all programming languages and Java is no exception. This allows a strongly typed language and as a result many potential problems can be caught at compile time. This is good programming practice even if it isn't required by the language. Wushutwist