Can a java lambda have more than 1 parameter?

Multiple Parameters Deep-Dive

Custom Functional Interfaces

When you need to work with more than two parameters, creating a custom functional interface is the way to go. Do not forget to add the @FunctionalInterface annotation:

@FunctionalInterface
interface TriFunction<T, U, V, R> {
    R apply(T t, U u, V v);    // applying makeup to three people at once
}

TriFunction<Integer, Integer, Integer, Integer> volume = (x, y, z) -> x * y * z;  // calculate the volume but not of sound ;)
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More Parameters, More Power with jOOL Library

For more complex cases with more parameters, the jOOL library saves the day. It provides interfaces supporting up to 16 parameters, preventing interface explosion:

// Usage of Function16 in jOOL
Function16<...> function = (a1, a2, ..., a16) -> {...};  // first I was afraid, I was petrified!
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Naming Constraints and Reusing Functional Interfaces

Choose names that convey intent to avoid confusions with Java's java.util.function package. Embed default methods to enable reusable interfaces:

@FunctionalInterface
interface BetterBiFunction<T, U, R> {   // when BiFunction is not enough
    R apply(T t, U u);

    default void printTheResult(T t, U u) {   // Let's show the world your result
        System.out.println(apply(t, u));
    }
}
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Error Handling with Lambdas

Implement error handling within lambdas using try-catch blocks:

BiFunction<String, String, String> concat = (a, b) -> {
    try {
        return a.concat(b);
    } catch (NullPointerException e) {
        return "Oops! One of your strings seems to be lost.";  // "I lost my strings, have you seen them?"
    }
};
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Language Comparisons: Java vs Scala

Scala has built-in facilities for handling multi-parameter lambdas, unlike Java which often requires custom interfaces:

val sumThree = (x: Int, y: Int, z: Int) => x + y + z
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Through such comparisons, Java developers can gain insights on improving their use of lambda expressions in their own projects.

More on Lambda Usability

Exploit Existing Java Functional Interfaces

Getting familiar with and using the java.util.function package can save time:

BiConsumer<T, U> printer = (t, u) -> System.out.printf("T: %s, U: %s\n", t, u);  // its a print fest!
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Inlining Lambdas for Clarity

Inline lambdas can improve code readability and efficiency:

processData((x, y, z) -> x * y + z);   // does a lot, says little!
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Such an inline lambda could be part of a method call to process data, acting as a clear ad-hoc transformation.