Java中如何使用反射获取指定方法？

class Class {
 @CallerSensitive
 public Method getMethod(String name, Class<?>... parameterTypes)
 throws NoSuchMethodException, SecurityException {
 Objects.requireNonNull(name);
 SecurityManager sm = System.getSecurityManager();
 if (sm != null) {
 // 1. 检查方法权限
 checkMemberAccess(sm, Member.PUBLIC, Reflection.getCallerClass(), true);
 }
 // 2. 获取方法
 Method method = getMethod0(name, parameterTypes);
 if (method == null) {
 throw new NoSuchMethodException(methodToString(name, parameterTypes));
 }
 // 3. 返回方法的拷贝
 return getReflectionFactory().copyMethod(method);
 }
 @CallerSensitive
 public Method getDeclaredMethod(String name, Class<?>... parameterTypes)
 throws NoSuchMethodException, SecurityException {
 Objects.requireNonNull(name);
 SecurityManager sm = System.getSecurityManager();
 if (sm != null) {
 // 1. 检查方法是权限
 checkMemberAccess(sm, Member.DECLARED, Reflection.getCallerClass(), true);
 }
 // 2. 获取方法
 Method method = searchMethods(privateGetDeclaredMethods(false), name, parameterTypes);
 if (method == null) {
 throw new NoSuchMethodException(methodToString(name, parameterTypes));
 }
 // 3. 返回方法的拷贝
 return getReflectionFactory().copyMethod(method);
 }
}