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class.newInstance()在java9时被@Deprecated

今天在用jdk17的反射时, 发现神器newInstance()竟然已过时, 被@Deprecated了 查看源码:

    @SuppressWarnings("removal")
    @CallerSensitive
    @Deprecated(since="9")
    public T newInstance()
        throws InstantiationException, IllegalAccessException
    {......}

/**
     * Creates a new instance of the class represented by this {@code Class}
     * object.  The class is instantiated as if by a {@code new}
     * expression with an empty argument list.  The class is initialized if it
     * has not already been initialized.
     *
     * @deprecated This method propagates any exception thrown by the
     * nullary constructor, including a checked exception.  Use of
     * this method effectively bypasses the compile-time exception
     * checking that would otherwise be performed by the compiler.
     * The {@link
     * java.lang.reflect.Constructor#newInstance(java.lang.Object...)
     * Constructor.newInstance} method avoids this problem by wrapping
     * any exception thrown by the constructor in a (checked) {@link
     * java.lang.reflect.InvocationTargetException}.
     *
     * <p>The call
     *
     * <pre>{@code
     * clazz.newInstance()
     * }</pre>
     *
     * can be replaced by
     *
     * <pre>{@code
     * clazz.getDeclaredConstructor().newInstance()
     * }</pre>
     *
     * The latter sequence of calls is inferred to be able to throw
     * the additional exception types {@link
     * InvocationTargetException} and {@link
     * NoSuchMethodException}. Both of these exception types are
     * subclasses of {@link ReflectiveOperationException}.
     *
     * @return  a newly allocated instance of the class represented by this
     *          object.
     * @throws  IllegalAccessException  if the class or its nullary
     *          constructor is not accessible.
     * @throws  InstantiationException
     *          if this {@code Class} represents an abstract class,
     *          an interface, an array class, a primitive type, or void;
     *          or if the class has no nullary constructor;
     *          or if the instantiation fails for some other reason.
     * @throws  ExceptionInInitializerError if the initialization
     *          provoked by this method fails.
     * @throws  SecurityException
     *          If a security manager, <i>s</i>, is present and
     *          the caller's class loader is not the same as or an
     *          ancestor of the class loader for the current class and
     *          invocation of {@link SecurityManager#checkPackageAccess
     *          s.checkPackageAccess()} denies access to the package
     *          of this class.
     */
    @SuppressWarnings("removal")
    @CallerSensitive
    @Deprecated(since="9")
    public T newInstance()
        throws InstantiationException, IllegalAccessException
    {
        SecurityManager sm = System.getSecurityManager();
        if (sm != null) {
            checkMemberAccess(sm, Member.PUBLIC, Reflection.getCallerClass(), false);
        }

        // Constructor lookup
        Constructor<T> tmpConstructor = cachedConstructor;
        if (tmpConstructor == null) {
            if (this == Class.class) {
                throw new IllegalAccessException(
                    "Can not call newInstance() on the Class for java.lang.Class"
                );
            }
            try {
                Class<?>[] empty = {};
                final Constructor<T> c = getReflectionFactory().copyConstructor(
                    getConstructor0(empty, Member.DECLARED));
                // Disable accessibility checks on the constructor
                // access check is done with the true caller
                java.security.AccessController.doPrivileged(
                    new java.security.PrivilegedAction<>() {
                        public Void run() {
                                c.setAccessible(true);
                                return null;
                            }
                        });
                cachedConstructor = tmpConstructor = c;
            } catch (NoSuchMethodException e) {
                throw (InstantiationException)
                    new InstantiationException(getName()).initCause(e);
            }
        }

        try {
            Class<?> caller = Reflection.getCallerClass();
            return getReflectionFactory().newInstance(tmpConstructor, null, caller);
        } catch (InvocationTargetException e) {
            Unsafe.getUnsafe().throwException(e.getTargetException());
            // Not reached
            return null;
        }
    }

使用 class.getDeclaredConstructor(...构造参数类).newInstance(...参数);

例如

Frame frame =
 	(Frame)Class.forName("java.awt.Frame")
 		.getDeclaredConstructor(String.class)
 			.newInstance("Frame标题");