Java – Stream has already been operated upon or closed
In Java 8, Stream cannot be reused, once it is consumed or used, the stream will be closed. If we reuse the stream it will throw an IllegalStateException, saying “stream…
Java – How to sum all the stream integers
The sum() method is available in the primitive int-value stream like IntStream, not Stream. We can use mapToInt() to convert a stream integers into a IntStream.
Java 8 – How to sort list with stream.sorted()
Few examples to show you how to sort a List with stream.sorted(): Sort a List with Comparator.naturalOrder(), Sort a List with Comparator.reverseOrder(), Sort a List user objects.
Java 8 – How to convert IntStream to int or int[]
Few Java 8 examples to get a primitive int from an IntStream. We can convert IntStream to primitive int array.
Java 8 – How to convert IntStream to Integer[]
How to convert IntStream to Integer array? The key is boxed() the IntStream into a Stream, then only convert to an Array.
Java 8 – Should we close the Stream after use?
Streams have a BaseStream.close() method and implement AutoCloseable, but nearly all stream instances do not actually need to be closed after use. Generally, only streams whose source is an IO…
Java 8 Stream – The peek() is not working with count()?
Many examples are using the .count() as the terminal operation for .peek(). However, for Java 9 and above, the peek() may print nothing. Since Java 9, if JDK compiler is…
Java 8 Stream – Convert List of List Strings to List Strings
As title, we can use flatMap to convert it. Similar to convert 2D array to 1D array using Stream.flatMap.
Java 8 Stream – Read a file line by line
In Java 8, you can use Files.lines to read file as Stream. A new method lines() has been added since 1.8, it lets BufferedReader returns content as Stream.
Java 8 – How to Sum BigDecimal using Stream?
In Java 8, we can use the Stream.reduce() to sum a list of BigDecimal. Java example to sum a list of BigDecimal values, using a normal for loop and a…