Also, there is no trusted information on whether the parameter is final when compiled without the -parameters option. The most notable differences are that the parameter names are not provided when compiled without the -parameters option. The next two screen snapshots demonstrate running ParameterDisplayer against instances of ManyMethods compiled without and with the -parameters option. Private void addListOfStrings(final List strings) String toString() Private void addArrayOfStrings(String strings) * Class with numerous methods intended to be used in demonstrating JDK 8's new It is called ManyMethods and is shown next. Therefore, I have created a simple example class to aid with the demonstration. I had initially thought about running this class against a well-known class of the JDK, but realized that would not be too helpful because those classes are not likely to have been built with the -parameters option. Out.println("You must provide the fully qualified name of at least one class.") Public static void main(final String arguments) Return Modifier.isFinal(parameter.getModifiers()) Private static boolean isParameterFinal(final Parameter parameter) * true} if provided Parameter is 'final'. * parameter Parameter to be tested for 'final' modifier. * Indicate whether provided Parameter is final. Private static void writeHeader(final String headerText) Out.println("Unable to find class " + className) + " and " + (parameter.isVarArgs() ? "IS " : "is NOT ") + ", and parameterized type of " + parameter.getParameterizedType() + "final, type " + parameter.getType().getCanonicalName() + (isParameterFinal(parameter) ? " IS " : " is NOT ") + (parameter.isNamePresent() ? parameter.getName() : "Parameter Name not provided,") + " has " + method.getParameterCount() + " Parameters:") įinal Parameter parameters = method.getParameters() įor (final Parameter parameter : parameters) Get all class's declared methods (does not get inherited methods)įinal Method declaredMethods = clazz.getDeclaredMethods() įor (final Method method : declaredMethods) Private static void displayParametersMetadata(final String classesNames)įor (final String className : classesNames)įinal Class clazz = Class.forName(className) * parent classes those classes should be individually submitted). * protected, and public methods, but does not include methods inherited from * of the methods and constructors of the provided class (includes private, * Uses JDK 8 Parameter class to demonstrate metadata related to the parameters The Oracle TechNotes page on javac indicates how this additional method/constructor parameter data can be accessed at runtime: “Stores formal parameter names of constructors and methods in the generated class file so that the method .getParameters from the Reflection API can retrieve them.” The following code snippet (class called ParameterDisplayer) demonstrates this (emphasis is on the displayParametersMetadata(String) method). This -parameters option is also shown when one types javac -help as shown in the next screen snapshot. class files compiled in Java 8 by passing the -parameters option to the javac compiler. The additional parameter metadata can be included in. The lesson also points out that there may be some cases where parameter names have sensitive information that the developer does not want available in the compiled. class files increases the size of those files. This lesson also emphasizes that this is an optional feature because storing additional parameter metadata in. The lesson includes an example Java class MethodParameterSpy that can be run against a provided Java class to indicate characteristics of method and constructor parameters. The Java Tutorials‘ Reflection API trail includes a lesson called Obtaining Names of Method Parameters that discusses and demonstrates how to apply this new feature in Java 8. This feature allows Java applications to access this parameter metadata information at runtime via reflection. One of the lesser advertised new features of JDK 8 is the optional ability to include parameter metadata in compiled Java classes.
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