CODEWITHSUNDEEP
javacasting
deinocheirus
deinocheirus

Reputation: 1863

Java direct cast vs using a local variable to cast

DISCLAIMER: I'm not sure whether this question is answerable as it currently stands. If it is very difficult to answer or actually impossible, I'll repost a compilable example, but I currently don't have time.

Can someone tell me why this compiles:

public void addOutputConnLayer(OutputConnLayer mainOutputConnLayer) {
    for (Map.Entry<String, AbstractPanelController<? extends AbstractPanelModel,
            ? extends AbstractPanelView<? extends AbstractPanelModel>>> entry : subControllers.entrySet()) {
        if (entry.getValue() instanceof OutputConnLayerUser) {
            OutputConnLayerUser tmp = (OutputConnLayerUser)entry.getValue();
            tmp.addOutputConnLayer(mainOutputConnLayer);
        }
    }
}

Whereas I get an "OutputConnLayerUser cannot be resolved to a variable" error when I don't use a local variable? For example:

public void addOutputConnLayer(OutputConnLayer mainOutputConnLayer) {
    for (Map.Entry<String, AbstractPanelController<? extends AbstractPanelModel,
            ? extends AbstractPanelView<? extends AbstractPanelModel>>> entry : subControllers.entrySet()) {
        if (entry.getValue() instanceof OutputConnLayerUser) {
            (OutputConnLayerUser)(entry.getValue()).addOutputConnLayer(mainOutputConnLayer); //<--- this line produces the error
        }
    }
}

OutputConnLayerUser is an interface with a single method. It looks as follows:

public interface OutputConnLayerUser {

    public void addOutputConnLayer(OutputConnLayer ocl);
}

Upvotes: 0

Views: 661

Answers (3)

sidshu
sidshu

Reputation: 333

You are not casting properly. Missing another parenthesis here 

public void addOutputConnLayer(OutputConnLayer mainOutputConnLayer) {
    for (Map.Entry<String, AbstractPanelController<? extends AbstractPanelModel,
            ? extends AbstractPanelView<? extends AbstractPanelModel>>> entry : subControllers.entrySet()) {
        if (entry.getValue() instanceof OutputConnLayerUser) {
            **(**(OutputConnLayerUser)(entry.getValue())**)**.addOutputConnLayer(mainOutputConnLayer); //<--- this line produces the error
        }
    }
}

Upvotes: 1

Uwe Plonus
Uwe Plonus

Reputation: 9954

You have to do a proper cast:

public void addOutputConnLayer(OutputConnLayer mainOutputConnLayer) {
    for (Map.Entry<String, AbstractPanelController<? extends AbstractPanelModel,
            ? extends AbstractPanelView<? extends AbstractPanelModel>>> entry : subControllers.entrySet()) {
        if (entry.getValue() instanceof OutputConnLayerUser) {
            ((OutputConnLayerUser)(entry.getValue())).addOutputConnLayer(mainOutputConnLayer); //<--- this line produces the error
        }
    }
}

Please note the additional brackets in the line with the error. You have to cast first and then call the method.

Upvotes: 0

Gabriel Negut
Gabriel Negut

Reputation: 13960

((OutputConnLayerUser) entry.getValue()).addOutputConnLayer(mainOutputConnLayer);

Upvotes: 2

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