Java Class New Instance newInstance(String classname, Properties properties)

Description

Get a new instance of an object based on its classpath.

License

Open Source License

Parameter

Parameter	Description
classname	the name of a class.
properties	properties to feed to the constructor or method if accepted.

Return

an instance of the class created through its default (no-arg) constructor.

Declaration

public static Object newInstance(String classname, Properties properties) 

Method Source Code

//package com.java2s;
/*//from   ww w  .  j  a v a 2  s.c om
Copyright 2009 Semantic Discovery, Inc. (www.semanticdiscovery.com)
    
This file is part of the Semantic Discovery Toolkit.
    
The Semantic Discovery Toolkit is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
    
The Semantic Discovery Toolkit is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU Lesser General Public License for more details.
    
You should have received a copy of the GNU Lesser General Public License
along with The Semantic Discovery Toolkit.  If not, see <http://www.gnu.org/licenses/>.
*/

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;

import java.util.Properties;

public class Main {
    /**
     * Get a new instance of an object based on its classpath.
     *
     * @param classname  the name of a class.
     * @param properties      properties to feed to the constructor or method
     *                        if accepted.
     *
     * @return an instance of the class created through its default (no-arg) constructor.
     */
    public static Object newInstance(String classname, Properties properties) {
        Object result = null;
        Class<?> theClass = null;

        try {
            theClass = Class.forName(classname);
            final Constructor constructor = theClass.getConstructor(Class.forName("java.util.Properties"));
            result = constructor.newInstance(properties);
        } catch (NoSuchMethodException e) {
            // when can't find a constructor that takes properties, use default constructor.
            result = newInstance(theClass);
        } catch (InstantiationException e) {
            throw new IllegalArgumentException("Can't instantiate '" + classname + "' ...", e);
        } catch (IllegalAccessException e) {
            throw new IllegalArgumentException("Can't access '" + classname + "' ...", e);
        } catch (ClassNotFoundException e) {
            throw new IllegalArgumentException("Can't find '" + classname + "' ...", e);
        } catch (InvocationTargetException e) {
            throw new IllegalArgumentException("Can't invoke '" + classname + ".newInstance(properties)' ...", e);
        } catch (NullPointerException e) {
            throw new IllegalArgumentException("Null instance '" + classname + "' ...", e);
        }

        return result;
    }

    /**
     * Get a new instance of an object based on its classpath.
     *
     * @param classname  the name of a class.
     *
     * @return an instance of the class created through its default (no-arg) constructor.
     */
    public static Object newInstance(String classname) {
        Object result = null;

        try {
            final Class theClass = Class.forName(classname);
            result = newInstance(theClass);
        } catch (ClassNotFoundException e) {
            throw new IllegalArgumentException("Can't find '" + classname + "' ...", e);
        } catch (NullPointerException e) {
            throw new IllegalArgumentException("Null instance '" + classname + "' ...", e);
        }

        return result;
    }

    /**
     * Get a new instance of an object based on its class.
     *
     * @param theClass  the class.
     *
     * @return an instance of the class created through its default (no-arg) constructor.
     */
    public static Object newInstance(Class theClass) {
        Object result = null;

        try {
            result = theClass.newInstance();
        } catch (InstantiationException e) {
            throw new IllegalArgumentException("Can't instantiate '" + theClass + "' ...", e);
        } catch (IllegalAccessException e) {
            throw new IllegalArgumentException("Can't access '" + theClass + "' ...", e);
        } catch (NullPointerException e) {
            throw new IllegalArgumentException("Null instance '" + theClass + "' ...", e);
        }

        return result;
    }
}

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1. newInstance(String className, Object... parameters)
2. newInstance(String className, Object... params)
3. newInstance(String className, Object[] args)
4. newInstance(String className, Object[] args)
5. newInstance(String className, Object[] args)
6. newInstance(String clazz)
7. newInstance(String clazzStr)
8. newInstance(String cls, Class interfaceType)
9. newInstance(String klass)