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Almost Named Method Arguments in JDK 8

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Almost Named Method Arguments in JDK 8

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Sometimes it would be really nice to have named method parameter in Java, this doesn't look likely for a long while but there is always another little work around, for example using a builder pattern to get similar behaviour, that will bridge the gap for a little bit. It occurred to me that using the Lambda support in JDK 8 you could get something very close without the boiler plate required by some of the other methods.

So consider this simple Facade class, that presents a method with a variable list of parameters. Note the variant of the method that takes in a Consumer object - this is what we are going to invoke with a Lambda later on.

package client;

import java.util.function.Consumer;

public class Facade {
    
    public static void invoke(Consumer<Parameter> op) {
        
        Parameter p = new Parameter();
        op.accept(new Parameter());
        invoke(p);        
    }
    
    public static void invoke(Parameter p) {

        // Defensive copy and validate
        p = p.clone();
        p.validate();
        
        // ...
    }

    
    public static class Parameter implements Cloneable {
        public String value1, value2, value3;
        
        public Parameter validate() {
            // ...
            
            return this;
        }

        public Parameter clone() {
            // We can use vanilla clone here, for more complicated mutable objects
            // you might need to perform a deeper copy
            try {
                return (Parameter) super.clone();
            } catch (CloneNotSupportedException e) {
                throw new RuntimeException(e);
            }
        }
    }
    
}

So once you have this in place, you can use Lambda notation to call the invoke method with how every many parameters as you might think suitable:

...
{

    public static void main(String[] args) {
        
        // Single parameter version
        Facade.invoke(p ->  p.value1="x" );
        // Multiple parameter version
        Facade.invoke(p -> { p.value1="x"; p.value2="y";});
    }
}

Of course the eagle eyed of your will recognise that the same pattern, minus the Consumermethod of course, with an earlier JDK. Given the number of java developers out there some-one probably will have probably already invented this pattern; but you never know and if you don't write it down the thought it didn't happen.

...
{

    public static void main(String[] args) {
        
        // Using an anonymous inner class pre JDK 8
        Facade.invoke(new Parameter() {{
            value1 = "x";
            value2 = "y";
        }});
    }
}


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Published at DZone with permission of Gerard Davison, DZone MVB. See the original article here.

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