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3.18 Converting Anonymous Inner Class to Lambda

Juppies 2 by Dr Heinz M. Kabutz

Java has often been accused of being too verbose. This has advantages and disadvantages. Its verbosity means that humans do not need to interpret what the code does - it is obvious for all to see.

Our anonymous inner classes are rather verbose. In the ORIGINAL_SCRAMBLER, we already know that we are making a Scrambler, because that is the type of the field declared on the left-hand side. So why do we have to repeat it? We also know that if there is only a single abstract method in the interface, it is very likely going to be this one that we are implementing. So why do we have to repeat the name of the interface in new Scrambler() and why do we need to explicitly state the name of the method scramble(char[] letters) when it is obvious that this would be the only method we could be implementing. We can deduce all that by just seeing that the type of the field is a Scrambler.

Since we have only one abstract method in our interface, we can replace the anonymous type with a lambda.

When making the lambda for the ORIGINAL_SCRAMBLER, we notice that we cannot put the curly braces and the comment on a single line. The reason is that when we write a comment with // anything on the right side of that is considered a comment, even our closing curly brace. This type of comment is called an end-of-line comment. We can also use a "traditional comment", which is like in C where we start with /* and end with */. By changing the comment we are able to wrap the comment with braces on a single line.

We also change the RANDOM_SCRAMBLER and the SORTED_SCRAMBLER to use lambdas instead of anonymous types.

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Heinz Kabutz Java Conference Speaker

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