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 – Convert String to double
In Java, we can use Double.parseDouble() to convert a String to primitive double, and we can use Double.valueOf() to convert a String to an Double object.
How to format a double in Java
In Java, we can use String.format or DecimalFormat to format a double, both support Locale based formatting.