A Human Readable Predicate with ObjectLab Kit

Recently, I have been working with Predicates.

I'm modelling some stuff for a bank but I needed to present updates and changes to the handwritten rules regularly. I don't know about you but wouldn't be nice if we could print the Predicate and not getting something like:

net.objectlab.kit.util.excel.ExcelWorkbookTest$$Lambda$1/868693306@13221655

Therefore, here comes the PrintablePredicate class in the next release of ObjectLab Kit.

See PrintablePredicate.java

The idea is to create an implementation of a Predicate and allow you to give it a name and the values it is comparing against.  We also support AND, OR and NEGATE as per a Predicate.

Let's imagine a small model, a financial Instrument 'Asset' and some basic Predicates.  Imagine that we create a predicate that detects instruments that are either Bonds or Commodities but that they should also be Active.

Using PrintablePredicate, I can combine 2 predicates and when I print the predicate (in an Excel spreadsheet that I generate automatically, more on that later) I can see a nice string "AssetClass in (Bond, Commodities) AND Active".  Here is the code for it:



This tiny class will come with ObjectLab Kit 1.4.1. Enjoy!

	package net.objectlab.kit.util.predicate;
	import java.util.ArrayList;
	import java.util.List;
	import java.util.function.Predicate;
	import lombok.AllArgsConstructor;
	import lombok.Data;
	import net.objectlab.kit.util.StringUtil;
	/**
	* Example for the PrintablePredicate.
	* Note that the example uses Lombok (highly recommended).
	* @author Benoit Xhenseval
	*/
	public class PrintablePredicateExample {
	@Data
	@AllArgsConstructor
	private static class Asset { // Using Lombok, replaces Get/Set and Constructor
	private String assetClass;
	private String assetType;
	private boolean active;
	}
	/** Predicate that tests for values Asset Class. */
	public static Predicate<Asset> hasAssetClass(String... assetClass) {
	return new PrintablePredicate<>("AssetClass",
	t -> StringUtil.equalsAnyIgnoreCase(t.getAssetClass(), assetClass),
	assetClass);
	}
	/** Predicate that tests if asset is active. */
	public static Predicate<Asset> isActive() {
	return new PrintablePredicate<>("Active", t -> t.isActive());
	}
	private static List<Asset> buildUniverse() {
	List<Asset> assets = new ArrayList<>();
	assets.add(new Asset("Equity", "Stock", true));
	assets.add(new Asset("Bond", "Government Bond", true));
	assets.add(new Asset("Bond", "Corporate Bond", true));
	assets.add(new Asset("Commodities", "Corn", true));
	assets.add(new Asset("Commodities", "Oil", false));
	return assets;
	}
	public static void main(String[] args) {
	List<Asset> assets = buildUniverse();
	final Predicate<Asset> activeBondOrCommidities = hasAssetClass("Bond", "Commodities").and(isActive());
	final long count = assets.stream().filter(activeBondOrCommidities).count(); // 3
	System.out.println(activeBondOrCommidities + " Returns " + count);
	// Prints "AssetClass in (Bond, Commodities) AND Active Returns 3"
	}
	}

view raw PrintablePredicateExample.java hosted with ❤ by GitHub