关于java:java-lamda表达式

@FunctionalInterfaceinterface FileHandle {    void doSome(String fileContent);}public class LamdaTest {    //能够了解为一种匿名函数的代替    //可选参数类型     //合乎lamda表达式的函数时接口：只有一个形象办法     //函数式接口注解@FunctionInterface 非必要    //函数式接口的形象办法签名：函数描述符     public static void handleFileContent(String url,FileHandle fileHandle) throws IOException {        BufferedReader bufferedReader = new BufferedReader(new FileReader(url));        String line;        StringBuilder stringBuilder = new StringBuilder();        while ((line = bufferedReader.readLine())!= null) {            stringBuilder.append(line + '\n');        }        fileHandle.doSome(stringBuilder.toString());    }    public static void main(String[] args) throws IOException {        LamdaTest.handleFileContent("D:\\hello.txt",str -> System.out.println(str.toUpperCase()));    }}