如何将java编译成class文件格式 .java编译成.class

/** 
	* @Description: 编译java文件
	* @author muzb
	* @date 2019年7月1日 上午9:42:16 
	* @param classRootPath class文件存放的根目录，com目录的上一层
	* @param javaFileList 待编辑的java文件集合
	* @return void 
	*/
	private static void compileJavaFile(String classRootPath, List<File> javaFileList) throws Exception {
		List<String> paths = new ArrayList<String>();
		for(File file : javaFileList){
			paths.add(file.getAbsolutePath());
		}
		JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
		DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<JavaFileObject>();
		StandardJavaFileManager fileManager = compiler.getStandardFileManager(diagnostics, null, Charset.forName("UTF-8"));
		Iterable<? extends JavaFileObject> compilationUnits = fileManager.getJavaFileObjectsFromStrings(paths);
		String libRootPath = "";//依赖jar包所在路径
		StringBuilder classPath = new StringBuilder();//编译依赖的class文件和jar包
		classPath.append(classRootPath).append(";");
		if("develop".equalsIgnoreCase(Global.env)){//开发环境
			libRootPath = BaseVo.class.getProtectionDomain().getCodeSource().getLocation().getFile();
			try {
				libRootPath = java.net.URLDecoder.decode(libRootPath, "UTF-8").replaceFirst("/", "").substring(0, libRootPath.indexOf("/com/"));
			} catch (UnsupportedEncodingException e1) {
				e1.printStackTrace();
			}
			classPath.append(libRootPath).append("org\\springframework\\spring-web\\4.0.0.RELEASE\\spring-web-4.0.0.RELEASE.jar;");
			classPath.append(libRootPath).append("org\\springframework\\spring-beans\\4.0.0.RELEASE\\spring-beans-4.0.0.RELEASE.jar;");
			classPath.append(libRootPath).append("org\\springframework\\spring-context\\4.0.0.RELEASE\\spring-context-4.0.0.RELEASE.jar;");
		}else if("product".equalsIgnoreCase(Global.env)){//生产环境
			libRootPath = classRootPath.substring(0, classRootPath.length()-7)+"lib\\";
			classPath.append(libRootPath).append("spring-web-4.0.0.RELEASE.jar;");
			classPath.append(libRootPath).append("spring-beans-4.0.0.RELEASE.jar;");
			classPath.append(libRootPath).append("spring-context-4.0.0.RELEASE.jar;");
		}
		//-d：输出class文件路径 -cp：依赖的class文件和jar包路径
		Iterable<String> options = Arrays.asList("-d", classRootPath,"-cp",classPath.toString()); //编译选项
		
		JavaCompiler.CompilationTask task = compiler.getTask(null, fileManager, diagnostics, options, null, compilationUnits);
		boolean result = task.call();
		if(!result){
			//编译结果为false，输出编译出错信息
			for (Diagnostic<?> diagnostic : diagnostics.getDiagnostics()) {
				logger.error(diagnostic.getSource().toString()+"/"+diagnostic.getLineNumber()+"/"+diagnostic.getMessage(null));
			}
		}
		try {
			fileManager.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}