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Questions and Answers
What is a functional interface in Java 8?
What is a functional interface in Java 8?
An interface with exactly one abstract method that matches the parameter and return types of a lambda expression.
What is the purpose of the java.util.function package?
What is the purpose of the java.util.function package?
To contain general purpose functional interfaces that can be used by end users.
Is an interface annotated with @FunctionalInterface required for the Java compiler to determine the interface as functional?
Is an interface annotated with @FunctionalInterface required for the Java compiler to determine the interface as functional?
No, it is not required but it helps to identify accidental violations of design intent.
What are the rules for @FunctionalInterface?
What are the rules for @FunctionalInterface?
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What is the purpose of the Predicate<T> interface in java.util.function?
What is the purpose of the Predicate<T> interface in java.util.function?
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What are some use cases for Predicate<T>?
What are some use cases for Predicate<T>?
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What are some default methods of the Predicate<T> interface?
What are some default methods of the Predicate<T> interface?
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What types of primitive functional interfaces does Java 8 introduce?
What types of primitive functional interfaces does Java 8 introduce?
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Study Notes
Functional Interfaces and Method References in Java 8
- A functional interface in Java 8 is an interface with exactly one abstract method that matches the parameter and return types of a lambda expression.
- The java.util.function package contains general purpose functional interfaces that can be used by end users.
- An interface annotated with @FunctionalInterface is not required for the Java compiler to determine the interface as functional, but it helps to identify accidental violations of design intent.
- Rules for @FunctionalInterface include having exactly one abstract method, allowing any number of default methods, and allowing the interface to override a public method.
- The Predicate<T> interface in java.util.function has a boolean-valued function that takes an argument and returns a boolean value.
- Predicate<T> can be used to identify odd numbers from a given set or find specific employees from a list of employees.
- Predicate<T> has default methods for logical AND, logical OR, and logical negation.
- Java 8 introduces primitive functional interfaces, which deal with only three primitive types: int, long, and double.
- Primitive functional interfaces avoid the extra cost associated with boxing and unboxing of generic types.
- Method references provide an efficient way to build lambda expressions that call existing methods.
- There are three types of method references: reference to static method, reference to an instance method of a particular object, and reference to an instance method of an arbitrary object of a particular type.
- Method references can also be used for constructors, with the syntax being the same as for static methods.
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Description
Test your knowledge of functional interfaces and method references in Java 8 with this quiz! Learn about the java.util.function package and its general purpose functional interfaces, the rules for @FunctionalInterface, and the benefits of using primitive functional interfaces. Discover how to identify odd numbers or specific employees using the Predicate<T> interface, and explore the different types of method references for building efficient lambda expressions. This quiz is perfect for Java developers looking to expand their understanding of functional programming in Java 8.
