The local variable might not have been initialized - Detect unchecked exception throw within a method

Question

I have some code with this structure:

public void method() {
    Object o;
    try {
        o = new Object();
    } catch (Exception e) {
        //Processing, several lines
        throw new Error(); //Our own unchecked exception
    }
    doSomething(o);
}

I have quite a few methods in which I have the same code in the catch block, so I want to extract it to a method so that I can save some lines. My problem is, that if I do that, I get a compiler error " The local variable o might not have been initialized".

public void method() {
    Object o;
    try {
        o = new Object();
    } catch (Exception e) {
        handleError();
    }
    //doSomething(o); compiler error
}


private void handleError() throws Error {
    //Processing, several lines
    throw new Error();
}

Is there any workaround?

Note:Instance variable not need to initialize but the local variable(variable inside a method) need to initialize — gjman2, Aug 07 '13 at 09:25

score 8 · Accepted Answer · answered Aug 07 '13 at 09:15

8

You need to initialize local variables before they are used as below

public void method() {
    Object o=null;
    try {
        o = new Object();
    } catch (Exception e) {
        handleError();
    }
   doSomething(o); 
}

You will not get the compilation failure until you use local variable which was not initialized

answered Aug 07 '13 at 09:15

Sanjaya Liyanage

4,366
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1

Not really suitable if the variable has to be final for some reason. In this case I would favor the solution provided by @gyro-gearless. – Eusebius Sep 09 '15 at 10:51
This feels so gross. Is there no better style? – theonlygusti Dec 05 '19 at 17:00

score 4 · Answer 2 · answered Aug 07 '13 at 09:15

4

Initialize your object: Object o = null;, however watch out for the NullPointerExceptions that might be thrown when you give it to the method calls.

answered Aug 07 '13 at 09:15

Juvanis

25,000
3
61
84

sanbhat · Answer 3 · 2013-08-07T09:20:05.507

3

Since o is getting initialized within the try block and initializing o might throw an exception, java thinks that doSomething(o) statement might reach without o being initialized. So java wants o to be initialized incase new Object() throws exception.

So initializing o with null will fix the issue

public void method() {
    Object o = null;
    try {
        o = new Object(); //--> If new Object() throws exception then o remains uninitialized
    } catch (Exception e) {
        handleError();
    }
    if(o != null)
      doSomething(o);
}

edited Aug 07 '13 at 09:20

answered Aug 07 '13 at 09:14

sanbhat

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I'd consider this an anti-pattern, as it clutters the code with unnecessary if-not-null checks! The try/catch mechanism is there to avoid such pattern: if the creation of some required objects fails, the function should leave through an exception. – Gyro Gearless Aug 07 '13 at 09:35
True, i agree. My intention was to give the solution and explain why we get error – sanbhat Aug 07 '13 at 09:42

score 3 · Answer 4 · answered Aug 07 '13 at 09:23

Just put the doSomething(o) inside the try { } block:

public void method() {
    Object o;
    try {
        o = new Object();
        doSomething(o);
    } catch (Exception e) {
        handleError();
    }

}

You perhaps dont want to execute doSomething() if the creation of your Object fails!

score 0 · Answer 5 · answered Aug 07 '13 at 09:37

0

Instance variable is the Object type so you should initialize value "null"

public void method() {
Object o=null;
try {
    o = new Object();
} catch (Exception e) {
    handleError();
}
doSomething(o); 
}

answered Aug 07 '13 at 09:37

Mohsin Shaikh

496
1
3
11

The local variable might not have been initialized - Detect unchecked exception throw within a method

5 Answers5

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