undo removing unused method to support legacy projects

spring-core/src/main/java/org/springframework/util/FileCopyUtils.java

@@ -112,7 +112,7 @@ public static int copy(InputStream in, OutputStream out) throws IOException {
 			int count = (int) in.transferTo(out);
 			out.flush();
 			return count;
-        }
+		}
 	}
 
 	/**

spring-core/src/main/java/org/springframework/util/StreamUtils.java

@@ -139,6 +139,29 @@ public static void copy(String in, Charset charset, OutputStream out) throws IOE
 		writer.flush();
 	}
 
+	/**
+	 * Copy the contents of the given InputStream to the given OutputStream.
+	 * <p>Leaves both streams open when done.
+	 * @param in the InputStream to copy from
+	 * @param out the OutputStream to copy to
+	 * @return the number of bytes copied
+	 * @throws IOException in case of I/O errors
+	 */
+	public static int copy(InputStream in, OutputStream out) throws IOException {
+		Assert.notNull(in, "No InputStream specified");
+		Assert.notNull(out, "No OutputStream specified");
+
+		int byteCount = 0;
+		byte[] buffer = new byte[BUFFER_SIZE];
+		int bytesRead;
+		while ((bytesRead = in.read(buffer)) != -1) {
+			out.write(buffer, 0, bytesRead);
+			byteCount += bytesRead;
+		}
+		out.flush();
+		return byteCount;
+	}
+
 	/**
 	 * Copy a range of content of the given InputStream to the given OutputStream.
 	 * <p>If the specified range exceeds the length of the InputStream, this copies

spring-core/src/test/java/org/springframework/util/StreamUtilsTests.java

@@ -83,6 +83,13 @@ void copyString() throws Exception {
 		assertThat(out.toByteArray()).isEqualTo(string.getBytes(charset));
 	}
 
+	@Test
+	void copyStream() throws Exception {
+		ByteArrayOutputStream out = new ByteArrayOutputStream();
+		StreamUtils.copy(new ByteArrayInputStream(bytes), out);
+		assertThat(out.toByteArray()).isEqualTo(bytes);
+	}
+
 	@Test
 	void copyRange() throws Exception {
 		ByteArrayOutputStream out = new ByteArrayOutputStream();

spring-web/src/main/java/org/springframework/http/converter/ByteArrayHttpMessageConverter.java

@@ -16,7 +16,6 @@
 
 package org.springframework.http.converter;
 
-import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 
 import org.springframework.http.HttpInputMessage;