Elvis.java

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Optional;
import java.util.Random;
import java.util.function.Supplier;

/*
================= RESULTS =================
=============================
NpeCatchDeepGetter:
dt = 200, c = 8190023
dt = 170, c = 8190023
dt = 153, c = 8190023
dt = 149, c = 8190023
dt = 143, c = 8190023
dt = 131, c = 8190023
dt = 152, c = 8190023
dt = 147, c = 8190023
dt = 144, c = 8190023
dt = 139, c = 8190023
Call statistics (except the first 5 calls): LongSummaryStatistics{count=5, sum=713, min=131, average=142.600000, max=152}
=============================
IfDeepGetter:
dt = 180, c = 8190023
dt = 142, c = 8190023
dt = 136, c = 8190023
dt = 133, c = 8190023
dt = 162, c = 8190023
dt = 149, c = 8190023
dt = 150, c = 8190023
dt = 148, c = 8190023
dt = 147, c = 8190023
dt = 145, c = 8190023
Call statistics (except the first 5 calls): LongSummaryStatistics{count=5, sum=739, min=145, average=147.800000, max=150}
=============================
LambdaElvisDeepGetter:
dt = 969, c = 8190023
dt = 611, c = 8190023
dt = 644, c = 8190023
dt = 604, c = 8190023
dt = 732, c = 8190023
dt = 659, c = 8190023
dt = 669, c = 8190023
dt = 370, c = 8190023
dt = 620, c = 8190023
dt = 367, c = 8190023
Call statistics (except the first 5 calls): LongSummaryStatistics{count=5, sum=2685, min=367, average=537.000000, max=669}
=============================
TernaryDeepGetter:
dt = 237, c = 8190023
dt = 239, c = 8190023
dt = 171, c = 8190023
dt = 177, c = 8190023
dt = 191, c = 8190023
dt = 174, c = 8190023
dt = 190, c = 8190023
dt = 198, c = 8190023
dt = 172, c = 8190023
dt = 168, c = 8190023
Call statistics (except the first 5 calls): LongSummaryStatistics{count=5, sum=902, min=168, average=180.400000, max=198}
=============================
LambdaNpeCatchDeepGetter:
dt = 262, c = 8190023
dt = 199, c = 8190023
dt = 211, c = 8190023
dt = 199, c = 8190023
dt = 208, c = 8190023
dt = 192, c = 8190023
dt = 196, c = 8190023
dt = 209, c = 8190023
dt = 227, c = 8190023
dt = 237, c = 8190023
Call statistics (except the first 5 calls): LongSummaryStatistics{count=5, sum=1061, min=192, average=212.200000, max=237}
 */

 /** @author Yahor Radtsevich */
public class Elvis {

    private static final int N = 10_000_000;
    public static void main(String[] args) {
        A[] a = new A[N];
        Arrays.setAll(a, index -> randomA());

        for (DeepGetter deepGetter : new DeepGetter[]{new NpeCatchDeepGetter(), new IfDeepGetter(), new LambdaElvisDeepGetter(), new TernaryDeepGetter(), new LambdaNpeCatchDeepGetter()}) {
            List<Long> dtList = new ArrayList<>();
            System.out.println("=============================\n"
                    + deepGetter.getClass().getSimpleName() + ":");
            for (int i = 0; i < 10; i++) {
                long t0 = System.currentTimeMillis();
                int c = 0;
                for (int j = 0; j < N; j++) {
                    c += deepGetter.getLength(a[j]);
                }
                long dt = System.currentTimeMillis() - t0;
                dtList.add(dt);
                System.out.println("dt = " + dt + ", c = " + c);
            }
            System.out.println("Call statistics (except the first 5 calls): " + dtList.stream().skip(5).mapToLong(x -> x).summaryStatistics());
        }
    }

    private interface DeepGetter {
        int getLength(A a);
    }

    private static class LambdaElvisDeepGetter implements DeepGetter {
        public int getLength(A a) {
            return Optional.ofNullable(a)
                    .map(A::getB)
                    .map(B::getC)
                    .map(C::getS)
                    .map(String::length)
                    .orElse(0);
        }
    }
    private static class TernaryDeepGetter implements DeepGetter {
        public int getLength(A a) {
            return a == null ? 0
                    : a.getB() == null ? 0
                    : a.getB().getC() == null ? 0
                    : a.getB().getC().getS() == null ? 0
                    : a.getB().getC().getS().length();
        }
    }
    private static class IfDeepGetter implements DeepGetter {
        public int getLength(A a) {
            if (a != null) {
                B b = a.getB();
                if (b != null) {
                    C cc = b.getC();
                    if (cc != null) {
                        String s = cc.getS();
                        if (s != null) {
                            return s.length();
                        }
                    }
                }
            }
            return 0;
        }
    }
    private static class NpeCatchDeepGetter implements DeepGetter {
        public int getLength(A a) {
            try {
                return a.getB().getC().getS().length();
            } catch (NullPointerException e) {
                return 0;
            }
        }
    }

    private static class LambdaNpeCatchDeepGetter implements DeepGetter {
        public int getLength(A a) {
            return NpeSafeLambda.get(() -> a.getB().getC().getS().length());
        }
    }

    static class NpeSafeLambda {
        static Integer get(Supplier<Integer> f) {
            try {
                return f.get();
            } catch (NullPointerException e) {
                return 0;
            }
        }
    }



    private static Random random = new Random(1);
    private static A randomA() {
        int rand = random.nextInt();
        A a = null;
        if ((rand & 0xF) != 0) { // probability = 15/16 = 0.9375
            a = new A();
            if ((rand & (0x7 << 4)) != 0) { // probability = 7/8 * 15/16 = 0.8203125
                B b = new B();
                a.setB(b);
                if ((rand & (0x3 << 7)) != 0) { // probability = 3/4 * 7/8 * 15/16 = 0.615234375
                    C c = new C();
                    b.setC(c);
                    if ((rand & (0x1 << 9)) != 0) { // probability = 1/2 * 3/4 * 7/8 * 15/16 = 0.3076171875
                        StringBuilder sBuilder = new StringBuilder(10);
                        for (int i = 0; i < random.nextInt(10); i++) {
                            sBuilder.append((char) (random.nextInt('Z' - 'A' + 1) + 'A'));
                        }
                        c.setS(sBuilder.toString());
                    }
                }
            }
        }
        return a;
    }

    private static class A {
        B b;

        public B getB() {
            return b;
        }

        public void setB(B b) {
            this.b = b;
        }
    }

    private static class B {
        C c;

        public C getC() {
            return c;
        }

        public void setC(C c) {
            this.c = c;
        }
    }

    private static class C {
        String s;

        public String getS() {
            return s;
        }

        public void setS(String s) {
            this.s = s;
        }
    }
}