In Jackson, we can use mapper.readValue(json, Map.class) to convert a JSON string to a Map
In Java 8, the Stream.reduce() combine elements of a stream and produces a single value, with 2 arguments: 1 – identity is default or initial value, and 2 – BinaryOperator is functional interface, take two values and produces a new value.
Few Java examples to show you how to filter a Map with Java 8 stream API. With Java 8, you can convert a Map.entrySet() into a stream, follow by a filter() and collect() it.
In Java 8, stream().map() lets you convert an object to something else. Review the following examples : convert a list of Strings to upper case, get all the name values from a list of the staff objects, convert a list of staff objects into a list of StaffPublic objects.
In Java 8, we can use the new forEach to loop or iterate a Map, List, Set, or Stream. Review the forEach method signature, it accepts a functional interface Consumer. We can use the Consumer method and pass it to the forEach method of List and Stream.
In Java, the System.getenv() returns an unmodifiable string Map view of the current system environment. If a requested environment variable is not defined, the System.getenv will return a null, and with Java 8 uses Optional to handle the null. The System.getenv() returns an unmodifiable string Map, modify the Map will cause UnsupportedOperationException.
Few Java examples to sort a Map by its keys or values: (1) Uses java.util.TreeMap, it will sort the Map by keys automatically, (2) Yet another java.util.TreeMap example, provide a custom Comparator to sort the key in descending order, (3) Sort by Value – Converts the Map into a List
Java 8 Stream examples to sort a Map, by keys or by values. Steps to sort a Map in Java 8: (1) Convert a Map into a Stream, (2) Sort it, (3) Collect and return a new LinkedHashMap (keep the order)
In Java, you can use System.getProperties() to get all the system properties. Also by sorting, you can display all the system properties in Alphabetical order.