JarCastingfunj
Collections and functional tools to complete the missing parts of Java/Guava.
To use with Maven:
<dependency>
<groupId>com.tek271</groupId>
<artifactId>funj</artifactId>
<version>1.0.2</version>
</dependency>
The maven central repo http://search.maven.org has the latest production version, while the latest code is in https://github.com/ahabra/funj
For the examples given below, suppose we have a class Cat
class Cat {
public long id;
public String name;
public int price;
private String color;
public String getColor() { return color; }
public void setColor(String color) { this.color = color; }
}
Additionally, suppose that we have a method getCats() which returns a list of Cats.
Notes
- You can access either getters/setters properties or fields by name directly.
- You can access nested properties and fields.
CollectionTools
toMap: Convert a collection to a map using one of collection's items properties as a key:
List<Cat> cats = getCats();
Map<Long, Cat> map = toMap(cats, "id");
Now the key in map is the id of Cat, while the value is the Cat object.
toMultimap: Group a collection by a property which is not unique:
com.google.common.collect.Multimap<String, Cat> multimap = toMultimap(cats, "color");
isEmpty: Check if a collection is null or empty:
isEmpty(cats)
Finder
findAll: Find a list of objects with a matching property value:
List<Cat> foundList = findAll(cats, "id", 1, 2);
will find cats whose id is either 1 or 2.
findFirst: Find the first object with a matching value of a property:
Cat found = findFirst(cats, "name", "tom");
will find the cat whose name property equals "tom"
reject: Return a list of objects whose value for propertyName is NOT any of the filter values
List<Cat> foundList = reject(cats, "name", "tom", "gar");
will find cats whose names is not "tom" nor "gar".
Mapper
pluck: Extract/pluck a property from a list of cats:
List<Long> ids = pluck(cats, "id");
pluckToSet: Extract/pluck a property from a list of cats and return a Set:
Set<String> colors = pluckToSet(cats, "color");
pluckKeyAndValue: Extract/pluck a key and value from a list of cats and create a map:
Map<Long, String> idsAndColors = pluckKeyAndValue(cats, "id", "color");
map: Map members of a list using a callback function:
Suppose that we have 3 cats with prices 10, 12, and 15. Also suppose that we have this callback function:
public int doubleThePrice(Cat cat, int maxPrice) {
return Math.min(cat.price * 2, maxPrice) ;
}
If you call map() like this:
List<Integer> prices = map(cats, this, "doubleThePrice", 25);
The prices list will be: [20, 24, 25].
Note The map() method is overloaded to support both static and dynamic callback methods.