JavaSE-反射-获取类或者对象的四种方法

Posted 2020-10-14 寻找风口的猪

1、使用Class类的静态方法Class.forName("xxxx");

　　新建一个要想要获取的类

package org.burning.sport.javase.classloader;

public class ClassLoaderModel {
}

package org.burning.sport.javase.classloader;

/**
 * 类的载入方式
 */
public class ClassLoaderMain {
    public static void main(String[] args) {

        ClassLoaderMain clm = new ClassLoaderMain();
        //1.使用Class静态方法Class.forName
        clm.loadClassMethod1();
    }

    public void loadClassMethod1() {
        try {
            Class<?> clazz = Class.forName("org.burning.sport.javase.classloader.ClassLoaderModel");
            ClassLoaderModel clm = (ClassLoaderModel)clazz.newInstance();
            System.out.println(clm);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

2、使用ClassLoader

package org.burning.sport.javase.classloader;

/**
 * 类的载入方式
 */
public class ClassLoaderMain {
    public static void main(String[] args) {
        ClassLoaderMain clm = new ClassLoaderMain();
        //2.使用ClassLoader
        clm.loadClassMethod2();
    }

    public void loadClassMethod2() {
        ClassLoader cl = this.getClass().getClassLoader();
        try {
            Class<?> clazz = cl.loadClass("org.burning.sport.javase.classloader.ClassLoaderModel");
            ClassLoaderModel clm = (ClassLoaderModel) clazz.newInstance();
            System.out.println(clm);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

 3、使用 类.class

package org.burning.sport.javase.classloader;

/**
 * 类的载入方式
 */
public class ClassLoaderMain {
    public static void main(String[] args) {
        ClassLoaderMain clm = new ClassLoaderMain();
        //3. 使用类.class方式
        clm.loadClassMethod3();

    }

    public void loadClassMethod3() {
        Class<?> clazz = ClassLoaderModel.class;
        try {
            ClassLoaderModel str = (ClassLoaderModel)clazz.newInstance();
            System.out.println(str);
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
    }
}

4、使用对象的getClass方法

package org.burning.sport.javase.classloader;


/**
 * Created by lisen on 2017/7/27.
 * 类的载入方式
 */
public class ClassLoaderMain {
    public static void main(String[] args) {
        ClassLoaderMain clm = new ClassLoaderMain();
        //4. 使用对象的getClass方法
        clm.loadClassMethod4();
    }

    public void loadClassMethod4() {
        ClassLoaderModel clm = new ClassLoaderModel();
        Class<?> clazz = clm.getClass();
        try {
            ClassLoaderModel ss = (ClassLoaderModel)clazz.newInstance();
            System.out.println(ss);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

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