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copied!<p>Lambdas are purely a call-site construct: the recipient of the lambda does not need to know that a Lambda is involved, instead it accepts an Interface with the appropriate method.</p> <p>In other words, you define or use a functional interface (i.e. an interface with a single method) that accepts and returns exactly what you want.</p> <p>For this Java 8 comes with a set of commonly-used interface types in <a href="http://docs.oracle.com/javase/8/docs/api/java/util/function/package-summary.html" rel="noreferrer"><code>java.util.function</code></a> (thanks to <a href="https://stackoverflow.com/users/1859863/maurice-naftalin">Maurice Naftalin</a> for the hint about the JavaDoc).</p> <p>For this specific use case there's <a href="http://docs.oracle.com/javase/8/docs/api/java/util/function/IntBinaryOperator.html" rel="noreferrer"><code>java.util.function.IntBinaryOperator</code></a> with <a href="http://docs.oracle.com/javase/8/docs/api/java/util/function/IntBinaryOperator.html#applyAsInt-int-int-" rel="noreferrer">a single <code>int applyAsInt(int left, int right)</code> method</a>, so you could write your <code>method</code> like this:</p> <pre><code>static int method(IntBinaryOperator op){ return op.applyAsInt(5, 10); } </code></pre> <p>But you can just as well define your own interface and use it like this:</p> <pre><code>public interface TwoArgIntOperator { public int op(int a, int b); } //elsewhere: static int method(TwoArgIntOperator operator) { return operator.op(5, 10); } </code></pre> <p>Using your own interface has the advantage that you can have names that more clearly indicate the intent.</p>

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