java reflect 学习

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1.如何实现从一个类名(如”java.util.ArrayList”)到类(ArrayList.class)再到实例化(Object,相当于new ArrayList())的过程转化？这个过程中需要处理哪些异常?

public class Demo1{       private int i = 1;       public static void main(String[] args){              try{                     Class class1 = Class.forName(“reflect.Demo1”);                     Demo1 demo1 = (Demo1)class1.newInstance();                     System.out.println(demo1.i);              }catch(ClassNotFoundException e) {                     e.printStackTrance();              }catch(InstatiationException e1) {                     e.printStackTrance();              }catch(IllegaAccessException e2) {                     e.printStackTrance();              }       }}

2.请说明如何获得一个对象的类名、包名？

public class Demo1{       public static void main(String[] args) {              String packageName = Demo1.class.getPackage().getName();              String objName = Demo1.class.getName();              String objSimpleName = Demo1.class.getSimpleName();       }}

3.请说明如何获得一个类（Class）的所有域（Field），包括其父类的域。

package reflect;import java.lang.reflect.Field;public class Father {       private String fname = "father";       private int fage = 40;       public static void main(String[] args) {              try {                     Class<Son> class1 = (Class<Son>) Class.forName("reflect.Son");                     Son son = class1.newInstance();                     Field[] fields = son.getClass().getDeclaredFields();   //getFields() 只能获得非private 以外的成员变量(czz注：不过实际运行时是可以获得private成员变量的)                     for (Field field : fields) {                            System.out.println(field.getName());                     }                     Field[] fields1 = son.getClass().getSuperclass().getDeclaredFields();                      for (Field field : fields1) {                            System.out.println(field.getName());                     }              } catch (ClassNotFoundException e) {                     // TODO Auto-generated catch block                     e.printStackTrace();              } catch (InstantiationException e) {                     // TODO Auto-generated catch block                     e.printStackTrace();              } catch (IllegalAccessException e) {                     // TODO Auto-generated catch block                     e.printStackTrace();              }                      }       public String getFname() {              return fname;       }       public void setFname(String fname) {              this.fname = fname;       }       public int getFage() {              return fage;       }       public void setFage(int fage) {              this.fage = fage;       }}class Son extends Father{       private String sname = "son";       private int sage = 20;       public String getSname() {              return sname;       }       public void setSname(String sname) {              this.sname = sname;       }       public int getSage() {              return sage;       }       public void setSage(int sage) {              this.sage = sage;       }}

4.请说明如何获得一个类（Class）的方法，以及如何调用这些方法？

package reflect;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;public class Demo3 {       public void show() {              System.out.println("show method");       }       public void show(int i) {              System.out.println("show method with param :" + i);       }       public int showReturn() {              return 1;       }       public static void main(String[] args) {              try {                     Class class1 = Class.forName("reflect.Demo3");                     Demo3 demo3 = (Demo3) class1.newInstance();                     Method method1 = demo3.getClass().getDeclaredMethod("show");                     Method method2 = demo3.getClass().getDeclaredMethod("show", int.class);                     Method method3 = demo3.getClass().getDeclaredMethod("showReturn");                     method1.invoke(demo3);                     method2.invoke(demo3, 2);                     Integer i = (Integer)method3.invoke(demo3);                     System.out.println(i);              } catch (ClassNotFoundException e) {                     // TODO Auto-generated catch block                     e.printStackTrace();              } catch (InstantiationException e) {                     // TODO Auto-generated catch block                     e.printStackTrace();              } catch (IllegalAccessException e) {                     // TODO Auto-generated catch block                     e.printStackTrace();              } catch (SecurityException e) {                     // TODO Auto-generated catch block                     e.printStackTrace();              } catch (NoSuchMethodException e) {                     // TODO Auto-generated catch block                     e.printStackTrace();              } catch (IllegalArgumentException e) {                     // TODO Auto-generated catch block                     e.printStackTrace();              } catch (InvocationTargetException e) {                     // TODO Auto-generated catch block                     e.printStackTrace();              }       }}