Java

This module provides important functions for interoperability with Java.

Usage¶

This modules allows Java executing specific code, such as instantiating a class, casting to another type, checking whether a value is an instance of a class, or throwing Java exceptions.

Representing a Java type¶

Function type takes a string - a fully qualified name of a Java class and creates a Yona representation of given class. This value can be used to create new instances of this type.

Example:

    big_integer = Java::type "java.math.BigInteger"

Creating a new instance of a Java class¶

Function new takes a Java type as the first argument and a sequence of arguments that are passed to the first matching constructor of the given type. Matching in this case means having same number of arguments, types are not checked.

Example:

    big_integer_two = Java::new big_integer ["2"]

Throwing Java exceptions¶

Function throw may be used to throw a Java exception. It takes an object as an argument and this object must be a Java Throwable.

Example:

let
    type = Java::type "java.lang.ArithmeticException"
    error = Java::new type ["testing error"]
in Java::throw error

Checking whether an object is instance of¶

Function instanceof takes an object and a type as arguments and returns a boolean if the object is instance of the provided type.

Example:

let
    type = Java::type "java.math.BigInteger"
    instance = Java::new type ["50"]
in Java::instanceof instance type

Casting an object to another type¶

Function case takes an object and a type to which the object should be casted to.

Example:

let
    type = Java::type "java.math.BigInteger"
    instance = Java::new type ["50"]
    cast_to_type = Java::type "java.lang.Number"
in Java::cast instance cast_to_type

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