Swap execution order of compile(String) and compile(Reader)

This allows us to compute a hash on the script as a String even if it was
input via the gererating Reader. We need to compute the hash for future
recompilation avoidance.

Signed-off-by: Squareys <Squareys@googlemail.com>

Author: Squareys

src/main/java/org/scijava/plugins/scripting/java/JavaEngine.java

@@ -168,22 +168,16 @@ public Object eval(Reader reader) throws ScriptException {
 	 * @return the compiled Java class as {@link Class}.
 	 */
 	public Class<?> compile(String script) throws ScriptException {
-		return compile(new StringReader(script));
-	}
-
-	/**
-	 * Compiles and runs the specified {@code .java} class.
-	 * 
-	 * @param reader the reader producing the source code for a Java class
-	 * @returns the compiled Java class as {@link Class}.
-	 */
-	public Class<?> compile(Reader reader) throws ScriptException {
 		final String path = (String)get(FILENAME);
 		File file = path == null ? null : new File(path);
 
 		final Writer writer = getContext().getErrorWriter();
 		try {
-			final Builder builder = new Builder(file, reader, writer);
+			// script may be null, but then we cannot create a StringReader for it,
+			// therefore null is passed if script is null.
+			final Builder builder =
+				new Builder(file, (script == null) ? null : new StringReader(script),
+					writer);
 			final MavenProject project = builder.project;
 			String mainClass = builder.mainClass;
 
@@ -221,6 +215,23 @@ public Class<?> compile(Reader reader) throws ScriptException {
 		return null;
 	}
 
+	/**
+	 * Compiles and runs the specified {@code .java} class.
+	 *
+	 * @param reader the reader producing the source code for a Java class
+	 * @returns the compiled Java class as {@link Class}.
+	 */
+	public Class<?> compile(Reader reader) throws ScriptException {
+		String script;
+		try {
+			script = getReaderContentsAsString(reader);
+		}
+		catch (IOException e) {
+			throw new ScriptException(e);
+		}
+		return compile(script);
+	}
+
 	/**
 	 * Compiles the specified {@code .java} file.
 	 *