Strategy Pattern with Lambda expressions.

MessingAround.java

package com.example;

import java.io.IOException;
import java.util.Arrays;
import java.util.List;
import java.util.function.Predicate;


public class MessingAround {

    public static int totalAssetValues(final List<Asset> assets,
                                       final Predicate<Asset> assetSelector) {
        return assets.stream().filter(assetSelector).mapToInt(Asset::getValue).sum();
    }

    public static void main(String[] args) throws IOException, InterruptedException {
        final List<Asset> assets = Arrays.asList(
                new Asset(Asset.AssetType.BOND, 1000),
                new Asset(Asset.AssetType.BOND, 2000),
                new Asset(Asset.AssetType.STOCK, 3000),
                new Asset(Asset.AssetType.STOCK, 4000)
        );

        System.out.println("Total of all assets: " + totalAssetValues(assets, asset -> true));
        System.out.println("Total of bonds: " +
                totalAssetValues(assets, asset -> asset.getType() == Asset.AssetType.BOND));
        System.out.println("Total of stocks: " +
                totalAssetValues(assets, asset -> asset.getType() == Asset.AssetType.STOCK));



    }
}