Java Programming Tutorials

Java programming tutorials with many code examples!

Java 8 count frequency of chars in String

Java interview question: In Java 8 count frequency of chars in a String. In this post we’ll show two implementations – using Map.merge() and Streams and Collectors.

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Java 8 List to Map

Very common task is creation of Map from a List of objects. In this post we show how to use Java 8 to convert List to Map using Collectors.

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Java 8 forEach examples

In this article we present Java 8 forEach on examples. These are very convenient methods for use with Lambda Expressions and method references.

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Java 8 reduce by example

Java 8 reduce is a great method to compute a value from stream of values – reduce collection to value. In this post we’ll explain how reduce in Java work.

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Java Util Optional map(Function)

java.util.Optional.map(Function)

The method Optional.map(Function) applies the given function to the optional value if it is present and returns an optional with the result or empty optional.

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Java Util Optional.ofNullable(T)

java.util.Optional.ofNullable(T)

The method Optional.ofNullable(T) returns Optional containing given value if it was not null or an empty Optional in case of null value.

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Java Util Map replaceAll(BiFunction)

java.util.Map.replaceAll(BiFunction)

The method Map.replaceAll(BiFunction) replaces each value with the result of applying the given function on the corresponding entry. Rethrows exceptions thrown by the replacement function.

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