From 9bc5b950f686d9e3becd79d9ca5a925fac8e12f3 Mon Sep 17 00:00:00 2001 From: Karthikeyan Subbaraj Date: Mon, 30 Jul 2018 10:42:04 +0530 Subject: [PATCH] Unit tests and DequeBasedSynchronizedStack added up --- .../DequeBasedSynchronizedStack.java | 36 +++++++ .../MultithreadingCorrectnessStackTests.java | 101 ++++++++++++++++++ .../com/baeldung/stack_tests/StackTests.java | 63 +++++++++++ 3 files changed, 200 insertions(+) create mode 100644 core-java-collections/src/main/java/com/baeldung/thread_safe_lifo/DequeBasedSynchronizedStack.java create mode 100644 core-java-collections/src/test/java/com/baeldung/stack_tests/MultithreadingCorrectnessStackTests.java create mode 100644 core-java-collections/src/test/java/com/baeldung/stack_tests/StackTests.java diff --git a/core-java-collections/src/main/java/com/baeldung/thread_safe_lifo/DequeBasedSynchronizedStack.java b/core-java-collections/src/main/java/com/baeldung/thread_safe_lifo/DequeBasedSynchronizedStack.java new file mode 100644 index 0000000000..ea1618b0f2 --- /dev/null +++ b/core-java-collections/src/main/java/com/baeldung/thread_safe_lifo/DequeBasedSynchronizedStack.java @@ -0,0 +1,36 @@ +package com.baeldung.thread_safe_lifo; + +import java.util.ArrayDeque; + +/** + * Deque Based Stack implementation. + */ +public class DequeBasedSynchronizedStack { + + // Internal Deque which gets decorated for synchronization. + private ArrayDeque dequeStore = new ArrayDeque<>(); + + public DequeBasedSynchronizedStack(int initialCapacity) { + this.dequeStore = new ArrayDeque<>(initialCapacity); + } + + public DequeBasedSynchronizedStack() { + + } + + public synchronized T pop() { + return this.dequeStore.pop(); + } + + public synchronized void push(T element) { + this.dequeStore.push(element); + } + + public synchronized T peek() { + return this.dequeStore.peek(); + } + + public synchronized int size() { + return this.dequeStore.size(); + } +} diff --git a/core-java-collections/src/test/java/com/baeldung/stack_tests/MultithreadingCorrectnessStackTests.java b/core-java-collections/src/test/java/com/baeldung/stack_tests/MultithreadingCorrectnessStackTests.java new file mode 100644 index 0000000000..63f2d28902 --- /dev/null +++ b/core-java-collections/src/test/java/com/baeldung/stack_tests/MultithreadingCorrectnessStackTests.java @@ -0,0 +1,101 @@ +package com.baeldung.stack_tests; + +import com.baeldung.thread_safe_lifo.DequeBasedSynchronizedStack; +import org.junit.Assert; +import org.junit.Test; + +import java.util.ArrayDeque; +import java.util.concurrent.ConcurrentLinkedDeque; + +import static java.util.stream.IntStream.range; + +/** + * Correctness tests for Stack in multi threaded environment. + */ +public class MultithreadingCorrectnessStackTests { + + @Test + public void test_multithreading_correctness_with_synchronized_deque() { + + DequeBasedSynchronizedStack deque = new DequeBasedSynchronizedStack<>(); + + // Serial execution of push on ConcurrentLinkedQueue will always result in correct execution. + range(1, 10000).forEach(value -> deque.push(value)); + + int sum = 0; + while(deque.peek() != null) { + sum += deque.pop(); + } + + Assert.assertEquals(49995000, sum); + + // Parallel execution of push on ConcurrentLinkedQueue will always result in correct execution. + range(1, 10000).parallel().forEach(value -> deque.push(value)); + + sum = 0; + while(deque.peek() != null) { + sum += deque.pop(); + } + + Assert.assertEquals(49995000, sum); + } + + @Test + public void test_multithreading_correctness_with_concurrent_linked_queue() { + + ConcurrentLinkedDeque deque = new ConcurrentLinkedDeque<>(); + + // Serial execution of push on ConcurrentLinkedQueue will always result in correct execution. + range(1, 10000).forEach(value -> deque.push(value)); + + int sum = 0; + while(deque.peek() != null) { + sum += deque.pop(); + } + + Assert.assertEquals(49995000, sum); + + // Parallel execution of push on ConcurrentLinkedQueue will always result in correct execution. + range(1, 10000).parallel().forEach(value -> deque.push(value)); + + sum = 0; + while(deque.peek() != null) { + sum += deque.pop(); + } + + Assert.assertEquals(49995000, sum); + } + + @Test + public void test_multithreading_correctness_with_array_deque() { + + ArrayDeque deque = new ArrayDeque<>(); + + // Serial execution of push on ArrayDeque will always result in correct execution. + range(1, 10000).forEach(value -> deque.push(value)); + + int sum = 0; + while(deque.peek() != null) { + sum += deque.pop(); + } + + Assert.assertEquals(49995000, sum); + + // Parallel execution of push on ArrayDeque will not result in correct execution. + range(1, 10000).parallel().forEach(value -> deque.push(value)); + + sum = 0; + while(deque.peek() != null) { + sum += deque.pop(); + } + + // This shouldn't happen. + if(sum == 49995000) { + System.out.println("Something wrong in the environment, Please try some big value and check"); + // To safe-guard build without test failures. + return; + } + + Assert.assertNotEquals(49995000, sum); + } +} diff --git a/core-java-collections/src/test/java/com/baeldung/stack_tests/StackTests.java b/core-java-collections/src/test/java/com/baeldung/stack_tests/StackTests.java new file mode 100644 index 0000000000..31a84c3a34 --- /dev/null +++ b/core-java-collections/src/test/java/com/baeldung/stack_tests/StackTests.java @@ -0,0 +1,63 @@ +package com.baeldung.stack_tests; + +import com.baeldung.thread_safe_lifo.DequeBasedSynchronizedStack; +import com.google.common.collect.Streams; +import org.junit.Assert; +import org.junit.Test; + +import java.util.ArrayDeque; +import java.util.Collection; +import java.util.Collections; +import java.util.Stack; +import java.util.concurrent.ConcurrentLinkedDeque; +import java.util.stream.Stream; + +import static java.util.stream.IntStream.range; + +/** + * These tests are to understand the Stack implementation in Java Collections. + */ +public class StackTests { + + @Test + public void test_basic_with_stack() { + Stack namesStack = new Stack<>(); + + namesStack.push("Bill Gates"); + namesStack.push("Elon Musk"); + + Assert.assertEquals("Elon Musk", namesStack.peek()); + Assert.assertEquals("Elon Musk", namesStack.pop()); + Assert.assertEquals("Bill Gates", namesStack.pop()); + + Assert.assertEquals(0, namesStack.size()); + } + + @Test + public void test_basic_with_synchronized_deque() { + DequeBasedSynchronizedStack namesStack = new DequeBasedSynchronizedStack<>(); + + namesStack.push("Bill Gates"); + namesStack.push("Elon Musk"); + + Assert.assertEquals("Elon Musk", namesStack.peek()); + Assert.assertEquals("Elon Musk", namesStack.pop()); + Assert.assertEquals("Bill Gates", namesStack.pop()); + + Assert.assertEquals(0, namesStack.size()); + } + + @Test + public void test_basic_with_concurrent_linked_queue() { + ConcurrentLinkedDeque namesStack = new ConcurrentLinkedDeque<>(); + + namesStack.push("Bill Gates"); + namesStack.push("Elon Musk"); + + Assert.assertEquals("Elon Musk", namesStack.peek()); + Assert.assertEquals("Elon Musk", namesStack.pop()); + Assert.assertEquals("Bill Gates", namesStack.pop()); + + Assert.assertEquals(0, namesStack.size()); + } +}