反射(一)获取变量，构造器，方法，获取类对象

反射---->获取变量，构造器，方法,获取类对象
	1.变量Field(实例或是静态变量) [获取，get,set]
	2.构造器Constructor[获取，new]
	3.方法Method
	4.类对象
	
1.变量 Field：
	1.获取
		1.class.getField("类中的成员变量名称"); (public 指定Field)
		2.class.getFields(); (public Fields)
		3.class.getDeclaredFields();(所有无关权限 Fields)
		4.class.getDeclaredField("类中的成员变量名称");(所有无关权限 Fields)
	2.基于获取后的get,set(obj 为实例)
		field.get(Object obj)
		field.set(Object obj,Object value)
演示：
	public static void main(String[] args) throws Exception {
		Class class1 = Calculate.class;
		Calculate obj = new Calculate();
		Field field = class1.getDeclaredField("name");
		System.out.println(field.get(obj));
		field.set(obj, "abc");
		System.out.println(obj);
	}
		
2.构造器Constructor:
	1.获取
		1.class.getConstructor(参数类s); (public 指定Constructor)
		2.class.getConstructors(); (public Constructors)
		3.class.getDeclaredConstructor(参数类s);(所有无关权限 Constructor)
		4.class.getDeclaredConstructors()(所有无关权限 Constructors)
	2.基于获取后的newInstance
		constructor.newInstance(具体参数);
	3.附加：如果是无参构造器:  class.newInstance();
演示：
	public static void main(String[] args) throws Exception {
		Class class1 = Calculate.class;
		Constructor constructor = class1.getConstructor(String.class
			,int.class);
		Object object = constructor.newInstance("美团",12);
		System.out.println(object);
	}
	
	public static void main(String[] args) throws Exception {
		Class class1 = Calculate.class;
		System.out.println(class1.newInstance());
	}
	
3.方法Method:
	1.获取
		1.class.getMethod(方法名String,参数类s); (public 指定Method)
		2.class.getMethods(); (public Methods)
		3.class.getDeclaredMethod(方法名String,参数类s);(所有无关权限 Methods)
		4.class.getDeclaredMethods()(所有无关权限 Methods)
	2.基于获取后的invoke (obj为实例)
		method.invoke(obj,具体参数s)
演示：
	public static void main(String[] args) throws Exception {
		Class class1 = Calculate.class;
		Calculate obj = new Calculate();
		Method method = class1.getMethod("add", int.class,int.class);
		System.out.println("result: "+method.invoke(obj, 3,4));
	}
4.类对象
	1.获取 (同一个类获取的类对象是相同的一个)
		1.Class.forName(全类名String);   多用于使用配置文件
		2.类名.class();
		3.对象.getClass();
演示：
	1.Class.forName(全类名String);   多用于使用配置文件	
		Class class1 = Class.forName("Day_8.Calculate");
	2.类名.class();	
		Class class2 = Day_8.Calculate.class;
	3.对象.getClass();
		Calculate calculate = new Calculate();
		Class class3 = calculate.getClass();
		
		System.out.println(class1 == class2 && class2 == class3);
		结果：true
		
附件：	
public class Calculate {
	private int a=5,b=3;
	private String name="helloWorld";
	public String ya = "a";
	public String ua = "a";
	public String ia = "a";
	public static int age = 10;
	
	public int add(int a,int b) {
		return a+b;
	}
	public int sub(int a,int b) {
		return a-b;
	}
	private String info() {
		return "it private func";
	}
	public Calculate(String name,int priority) {
		this.name = name;
		System.out.println(name+" is a priority "+priority+" calculator");
	}
	public Calculate(String name,String priority) {
		this(name,Integer.parseInt(priority));
	}
	
	public Calculate() {
		super();
	}
	@Override
	public String toString() {
		return "Calculate [a=" + a + ", b=" + b + ", name=" 
			+ name + ", ya=" + ya + ", ua=" + ua + ", ia=" + ia + "]";
	}
}