SimpleStopWatch is alternative for overcomplicated and buggy StopWatch

src/main/java/org/apache/commons/lang3/time/SimpleStopWatch.java

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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.apache.commons.lang3.time;
+
+/**
+ * <p>
+ * {@link SimpleStopWatch} provides a convenient API for timings.
+ * </p>
+ * <p>
+ * {@link SimpleStopWatch} is simple alternative for {@link StopWatch}. It does not have state flow
+ * and API is no-brainer.
+ * </p>
+ * <p>
+ * {@link SimpleStopWatch} use {@link System#nanoTime()} for time measure.
+ * </p>
+
+ *
+ * <p>
+ * To start the watch, call {@link SimpleStopWatch#started()}.
+ * </p>
+ * <p>
+ * To get time in millis since start, call {@link #time()}.
+ * </p>
+ * <p>
+ * {@link #lap()} returns time in millis since last {@link #lap()} call or since start
+ * when {@link #lap()} not called yet. For example:<br>
+ * 1. var stopWatch = SimpleStopWatch.started()<br>
+ * 2. sleep (200 ms)<br>
+ * 3. stopWatch.getTime() == 200, stopWatch.lap() == 200<br>
+ * 4. sleep (100 ms)<br>
+ * 5. stopWatch.getTime() == 300, stopWatch.lap() == 100<br>
+
+ * <p>This class is not thread-safe.</p>
+ *
+ * @since 3.12
+ */
+public class SimpleStopWatch {
+
+
+    private static final long NANO_2_MILLIS = 1000000L;
+
+    /**
+     * Creates a simple stop watch.<br>
+     * To avoid doubts for people used to {@link StopWatch} method name explains
+     * that SimpleStopWatch is started when created.
+     *
+     * @return SimpleStopWatch a stopwatch.
+     */
+    public static SimpleStopWatch started() {
+        return new SimpleStopWatch();
+    }
+
+
+    /**
+     * The start time in nanoseconds.
+     */
+    private long startTimeNanos;
+
+
+    /**
+     * The lap start time in nanoseconds.
+     */
+    private long lapStartTimeNanos;
+
+
+    private SimpleStopWatch() {
+        this.startTimeNanos = System.nanoTime();
+        this.lapStartTimeNanos = startTimeNanos;
+    }
+
+    /**
+     * <p>
+     * Gets the time on the stopwatch.
+     * </p>
+     *
+     * @return the time in milliseconds
+     */
+    public long time() {
+        return (System.nanoTime() - this.startTimeNanos) / NANO_2_MILLIS;
+    }
+
+    /**
+     * <p>
+     * Gets the time on the stopwatch since last ${lap} call or since start when ${lap} not called yet
+     * </p>
+     *
+     * @return the time in milliseconds
+     */
+    public long lap() {
+        long lapTime = (System.nanoTime() - lapStartTimeNanos) / NANO_2_MILLIS;
+        lapStartTimeNanos = System.nanoTime();
+        return lapTime;
+    }
+}

src/test/java/org/apache/commons/lang3/time/SimpleStopWatchTest.java

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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.apache.commons.lang3.time;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertAll;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * TestCase for SimpleStopWatch.
+ */
+class SimpleStopWatchTest {
+
+    @Test
+    void testSimpleStopWatch() throws InterruptedException {
+        SimpleStopWatch simpleStopWatch = SimpleStopWatch.started();
+
+        {
+            Thread.sleep(500);
+            long time500 = simpleStopWatch.time();
+            long lap500 = simpleStopWatch.lap();
+            assertAll(
+                    () -> assertTrue(time500 > 450, String.valueOf(time500)),
+                    () -> assertTrue(time500 < 550, String.valueOf(time500)),
+                    () -> assertTrue(lap500 > 450, String.valueOf(lap500)),
+                    () -> assertTrue(lap500 < 550, String.valueOf(lap500)));
+        }
+        {
+            Thread.sleep(300);
+            long time800 = simpleStopWatch.time();
+            long lap300 = simpleStopWatch.lap();
+
+            assertAll(
+                    () -> assertTrue(time800 > 750, String.valueOf(time800)),
+                    () -> assertTrue(time800 < 900, String.valueOf(time800)),
+                    () -> assertTrue(lap300 > 250,  String.valueOf(lap300)),
+                    () -> assertTrue(lap300 < 350,  String.valueOf(lap300)));
+        }
+    }
+}