Collectors toMap

Java-Collectors toMap

Collectors toMap The Collectors class provides a large number of static methods for common collectors. The toMap( ) method of the collectors is used to collect stream elements into a Map.  The toMap( ) method has three forms. The first is: If the mapped keys contain duplicates (according to Object.equals(Object)), an IllegalStateException is thrown when the collection … Read more…

Using Collector for Collection

Java-Using Collector for Collection

Using Collector for Collection The stream API provides the another form of collect( ) method. This method is used to obtain a collection from a stream using Collector interface. It has the following form: Here, R specifies the type of the result, and T specifies the element type of the invoking stream. The internal accumulated type … Read more…

Collection From a Stream

Java-Collection From a Stream

Collection From a Stream The stream API provides the collect( ) method. This method is used to obtain a collection from a stream. The ability to move data from a collection to a stream, and then back to a collection again is a very powerful attribute of the stream API. It gives you the ability … Read more…

Another Version of Reduce

Java-Another Version of Reduce

Another Version of Reduce Suppose you have a stream of objects and want to form the sum of some property, such as all lengths in a stream of strings. For example: In this case, you can’t use the simple form of reduce. It requires a function (T, T) -> T, with the same types for the … Read more…

Stream to Primitive Stream

Java-Stream to Primitive Stream

Stream to Primitive Stream The Stream class provides three methods that return a primitive stream from Stream. These three methods are: Consider the following program, it first creates an Stream of PlayerData. It then uses mapToInt( ) and mapToDouble( ) to create an IntStream and DoubleStream that are contains the each player weight and height. The … Read more…

Argument Index

Java-Argument Index

Argument Index Formatter includes a very useful feature that lets you specify the argument to which a format specifier applies. Normally, format specifiers and arguments are matched in order, from left to right. That is, the first format specifier matches the first argument, the second format specifier matches the second argument, and so on. However, … Read more…