Simplify conversion of ByteArrayOutputStream to String

Closes gh-24785

spring-context-indexer/src/main/java/org/springframework/context/index/processor/SortedProperties.java

@@ -88,7 +88,7 @@ class SortedProperties extends Properties {
 	public void store(OutputStream out, String comments) throws IOException {
 		ByteArrayOutputStream baos = new ByteArrayOutputStream();
 		super.store(baos, (this.omitComments ? null : comments));
-		String contents = new String(baos.toByteArray(), StandardCharsets.ISO_8859_1);
+		String contents = baos.toString(StandardCharsets.ISO_8859_1.name());
 		for (String line : contents.split(EOL)) {
 			if (!(this.omitComments && line.startsWith("#"))) {
 				out.write((line + EOL).getBytes(StandardCharsets.ISO_8859_1));

spring-core/src/main/java/org/springframework/core/SortedProperties.java

@@ -90,7 +90,7 @@ class SortedProperties extends Properties {
 	public void store(OutputStream out, @Nullable String comments) throws IOException {
 		ByteArrayOutputStream baos = new ByteArrayOutputStream();
 		super.store(baos, (this.omitComments ? null : comments));
-		String contents = new String(baos.toByteArray(), StandardCharsets.ISO_8859_1);
+		String contents = baos.toString(StandardCharsets.ISO_8859_1.name());
 		for (String line : contents.split(EOL)) {
 			if (!(this.omitComments && line.startsWith("#"))) {
 				out.write((line + EOL).getBytes(StandardCharsets.ISO_8859_1));

spring-messaging/src/main/java/org/springframework/messaging/converter/ProtobufMessageConverter.java

@@ -183,7 +183,7 @@ public class ProtobufMessageConverter extends AbstractMessageConverter {
 			else if (this.protobufFormatSupport != null) {
 				ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
 				this.protobufFormatSupport.print(message, outputStream, contentType, charset);
-				payload = new String(outputStream.toByteArray(), charset);
+				payload = outputStream.toString(charset.name());
 			}
 		}
 		catch (IOException ex) {

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/client/RestTemplateXhrTransport.java

@@ -252,15 +252,14 @@ public class RestTemplateXhrTransport extends AbstractXhrTransport {
 			return null;
 		}
 
-		private void handleFrame(ByteArrayOutputStream os) {
-			byte[] bytes = os.toByteArray();
+		private void handleFrame(ByteArrayOutputStream os) throws IOException {
+			String content = os.toString(SockJsFrame.CHARSET.toString());
 			os.reset();
-			String content = new String(bytes, SockJsFrame.CHARSET);
 			if (logger.isTraceEnabled()) {
 				logger.trace("XHR receive content: " + content);
 			}
 			if (!PRELUDE.equals(content)) {
-				this.sockJsSession.handleFrame(new String(bytes, SockJsFrame.CHARSET));
+				this.sockJsSession.handleFrame(content);
 			}
 		}
 	}