Java Class New Instance newInstance(Class theCls)

Description

Create an object for the given class.

License

Apache License

Parameter

Parameter	Description
theCls	class of which an object is created.

Return

a new object

Declaration

@SuppressWarnings("unchecked")
public static <T> T newInstance(Class<T> theCls) 

Method Source Code

//package com.java2s;
/*/*from w  ww.  j a va2s . c o  m*/
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 *
 */

import java.lang.reflect.Constructor;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

public class Main {
    private static final Map<Class<?>, Constructor<?>> constructorCache = new ConcurrentHashMap<Class<?>, Constructor<?>>();

    /**
     * Create an object for the given class.
     *
     * @param theCls
     *          class of which an object is created.
     * @return a new object
     */
    @SuppressWarnings("unchecked")
    public static <T> T newInstance(Class<T> theCls) {
        T result;
        try {
            Constructor<T> meth = (Constructor<T>) constructorCache.get(theCls);
            if (null == meth) {
                meth = theCls.getDeclaredConstructor();
                meth.setAccessible(true);
                constructorCache.put(theCls, meth);
            }
            result = meth.newInstance();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
        return result;
    }

    /**
     * Create an object using the given class name.
     *
     * @param clsName
     *          class name of which an object is created.
     * @param xface
     *          The interface implemented by the named class.
     * @return a new object
     */
    @SuppressWarnings("unchecked")
    public static <T> T newInstance(String clsName, Class<T> xface) {
        Class<?> theCls;
        try {
            theCls = Class.forName(clsName);
        } catch (ClassNotFoundException cnfe) {
            throw new RuntimeException(cnfe);
        }
        if (!xface.isAssignableFrom(theCls)) {
            throw new RuntimeException(clsName + " not " + xface.getName());
        }
        return newInstance(theCls.asSubclass(xface));
    }
}

Related

1. newInstance(Class theClass)
2. newInstance(Class theClass)
3. newInstance(Class theClass, Class[] parameterTypes, Object[] initargs)
4. newInstance(Class theClass, Object... initArgs)
5. newInstance(Class theClass, String className)
6. newInstance(Class type)
7. newInstance(Class type)
8. newInstance(Class type)
9. newInstance(Class type)