Revise synchronized blocks

- Replace synchronized with Lock when guarding long-running operations
- Remove unnecessary synchronization in FileSystemWatcher
- Replace HashMap with ConcurrentHashMap in Restarter
- Remove unnecessary locking on AtomicBoolean in
  SpringApplicationBuilder
- Remove unnecessary locking in SimpleFormatter

Closes gh-36670

spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/data/RandomAccessDataFile.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2022 the original author or authors.
+ * Copyright 2012-2023 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.
@@ -22,6 +22,8 @@ import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.RandomAccessFile;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
 
 /**
  * {@link RandomAccessData} implementation backed by a {@link RandomAccessFile}.
@@ -209,7 +211,7 @@ public class RandomAccessDataFile implements RandomAccessData {
 
 	private static final class FileAccess {
 
-		private final Object monitor = new Object();
+		private final Lock lock = new ReentrantLock();
 
 		private final File file;
 
@@ -221,11 +223,15 @@ public class RandomAccessDataFile implements RandomAccessData {
 		}
 
 		private int read(byte[] bytes, long position, int offset, int length) throws IOException {
-			synchronized (this.monitor) {
+			this.lock.lock();
+			try {
 				openIfNecessary();
 				this.randomAccessFile.seek(position);
 				return this.randomAccessFile.read(bytes, offset, length);
 			}
+			finally {
+				this.lock.unlock();
+			}
 		}
 
 		private void openIfNecessary() {
@@ -241,20 +247,28 @@ public class RandomAccessDataFile implements RandomAccessData {
 		}
 
 		private void close() throws IOException {
-			synchronized (this.monitor) {
+			this.lock.lock();
+			try {
 				if (this.randomAccessFile != null) {
 					this.randomAccessFile.close();
 					this.randomAccessFile = null;
 				}
 			}
+			finally {
+				this.lock.unlock();
+			}
 		}
 
 		private int readByte(long position) throws IOException {
-			synchronized (this.monitor) {
+			this.lock.lock();
+			try {
 				openIfNecessary();
 				this.randomAccessFile.seek(position);
 				return this.randomAccessFile.read();
 			}
+			finally {
+				this.lock.unlock();
+			}
 		}
 
 	}