Streams

Java Joy: Turn Stream Into An Array

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Hubert Klein Ikkink

The Java Stream API has many useful methods. If we want to transform a Stream to a Java array we can use the toArray method. Without an argument the result is an object array (Object[]), but we can also use an argument to return an array of another type. The easiest way is to use the contructor of the array type we want as method reference. Then the result is an array of the given type with the elements of the stream.

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Java Joy: Combining Predicates

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Hubert Klein Ikkink

In Java we can use a Predicate to test if something is true or false. This is especially useful when we use the filter method of the Java Stream API. We can use lambda expressions to define our Predicate or implement the Predicate interface. If we want to combine different Predicate objects we can use the or, and and negate methods of the Predicate interfaces. These are default methods of the interface and will return a new Predicate.

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