Fix metrics speed tests on Windows

Write to NUL on Windows and /dev/null on other platforms. Increase the
default number of iterations to avoid problems with the reduced timing
precision on Windows.

Closes gh-2976

spring-boot-actuator/src/test/java/org/springframework/boot/actuate/metrics/buffer/BufferGaugeServiceSpeedTests.java

@@ -69,7 +69,7 @@ public class BufferGaugeServiceSpeedTests {
 	private static int threadCount = 2;
 
 	private static final int number = Boolean.getBoolean("performance.test") ? 10000000
-			: 100000;
+			: 1000000;
 
 	private static StopWatch watch = new StopWatch("count");
 
@@ -79,7 +79,7 @@ public class BufferGaugeServiceSpeedTests {
 
 	@BeforeClass
 	public static void prime() throws FileNotFoundException {
-		err = new PrintWriter("/dev/null");
+		err = new NullPrintWriter();
 		final Random random = new Random();
 		for (int i = 0; i < 1000; i++) {
 			sample[i] = names[random.nextInt(names.length)];

spring-boot-actuator/src/test/java/org/springframework/boot/actuate/metrics/buffer/CounterServiceSpeedTests.java

@@ -67,7 +67,7 @@ public class CounterServiceSpeedTests {
 	private static int threadCount = 2;
 
 	private static final int number = Boolean.getBoolean("performance.test") ? 10000000
-			: 100000;
+			: 1000000;
 
 	private static StopWatch watch = new StopWatch("count");
 
@@ -77,7 +77,7 @@ public class CounterServiceSpeedTests {
 
 	@BeforeClass
 	public static void prime() throws FileNotFoundException {
-		err = new PrintWriter("/dev/null");
+		err = new NullPrintWriter();
 		final Random random = new Random();
 		for (int i = 0; i < 1000; i++) {
 			sample[i] = names[random.nextInt(names.length)];

spring-boot-actuator/src/test/java/org/springframework/boot/actuate/metrics/buffer/DefaultCounterServiceSpeedTests.java

@@ -67,7 +67,7 @@ public class DefaultCounterServiceSpeedTests {
 	private static int threadCount = 2;
 
 	private static final int number = Boolean.getBoolean("performance.test") ? 2000000
-			: 100000;
+			: 1000000;
 
 	private static int count;
 
@@ -77,7 +77,7 @@ public class DefaultCounterServiceSpeedTests {
 
 	@BeforeClass
 	public static void prime() throws FileNotFoundException {
-		err = new PrintWriter("/dev/null");
+		err = new NullPrintWriter();
 		final Random random = new Random();
 		for (int i = 0; i < 1000; i++) {
 			sample[i] = names[random.nextInt(names.length)];

spring-boot-actuator/src/test/java/org/springframework/boot/actuate/metrics/buffer/DefaultGaugeServiceSpeedTests.java

@@ -67,7 +67,7 @@ public class DefaultGaugeServiceSpeedTests {
 	private static int threadCount = 2;
 
 	private static final int number = Boolean.getBoolean("performance.test") ? 5000000
-			: 100000;
+			: 1000000;
 
 	private static int count;
 
@@ -77,7 +77,7 @@ public class DefaultGaugeServiceSpeedTests {
 
 	@BeforeClass
 	public static void prime() throws FileNotFoundException {
-		err = new PrintWriter("/dev/null");
+		err = new NullPrintWriter();
 		final Random random = new Random();
 		for (int i = 0; i < 1000; i++) {
 			sample[i] = names[random.nextInt(names.length)];

spring-boot-actuator/src/test/java/org/springframework/boot/actuate/metrics/buffer/DropwizardCounterServiceSpeedTests.java

@@ -70,7 +70,7 @@ public class DropwizardCounterServiceSpeedTests {
 	private static int threadCount = 2;
 
 	private static final int number = Boolean.getBoolean("performance.test") ? 10000000
-			: 100000;
+			: 1000000;
 
 	private static int count;
 
@@ -80,7 +80,7 @@ public class DropwizardCounterServiceSpeedTests {
 
 	@BeforeClass
 	public static void prime() throws FileNotFoundException {
-		err = new PrintWriter("/dev/null");
+		err = new NullPrintWriter();
 		final Random random = new Random();
 		for (int i = 0; i < 1000; i++) {
 			sample[i] = names[random.nextInt(names.length)];

spring-boot-actuator/src/test/java/org/springframework/boot/actuate/metrics/buffer/NullPrintWriter.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2012-2015 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.actuate.metrics.buffer;
+
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.PrintWriter;
+
+/**
+ * A {@link PrintWriter} that writes to {@code NUL} on Windows and {@code /dev/null} on
+ * all other platforms.
+ *
+ * @author Andy Wilkinson
+ */
+public class NullPrintWriter extends PrintWriter {
+
+	public NullPrintWriter() throws FileNotFoundException {
+		super(isWindows() ? "NUL" : "/dev/null");
+	}
+
+	private static boolean isWindows() {
+		return File.separatorChar == '\\';
+	}
+
+}