java 反射（reflect）总结。

/**
 * 获取一个Class类有三种方法：
 * @author Morgan
 */
public class GetClass {
	public static void main(String[] args) {
		
		//第一种获取方法，直接了当 
		Class<String> class1 = String.class;
		System.out.println(class1);
		
		//第二种获取方法，对实体类运用方法  
		String str = "just do it";  
		Class<?> class2 = str.getClass();
		System.out.println(class2);
		
		//第三种获取方法，直接传递一个类名，字符串形式  
		try {
			Class<?> class3 = Class.forName("java.lang.String");
			System.out.println(class3);
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}
		
		
	}
}

 

/**
 * 获取一个Filed字段类的，有四种方法
 * @author Morgan
 *
 */
public class GetFiled {
	public static void main(String[] args) {
		Class<String> class1 = String.class;
		
		//1.获取所有申明的字段  
		Field[] fields1 = class1.getDeclaredFields(); 
		for (Field field : fields1) {
			System.out.println(field);
		}
		
		System.out.println("------------------------------------------------");
		//2.获取所有的公共类字段  
		Field[] fields2 = class1.getFields();  
		for (Field field : fields2) {
			System.out.println(field);
		}
		System.out.println("------------------------------------------------");		          
		//3.获取指定字段名（所有申明的字段都可获取）  
		try {
			Field field1 = class1.getDeclaredField("value");
			System.out.println(field1);
		} catch (SecurityException e) {
			e.printStackTrace();
		} catch (NoSuchFieldException e) {
			e.printStackTrace();
		}  
		System.out.println("------------------------------------------------");		          
		//4.获取指定公共字段名  
		try {
			Field field2 = class1.getField("CASE_INSENSITIVE_ORDER");
			System.out.println(field2);
		} catch (SecurityException e) {
			e.printStackTrace();
		} catch (NoSuchFieldException e) {
			e.printStackTrace();
		}
	}
}

 

/**
 * Method类：同Field有四种方法
 * @author Morgan
 */
public class TestMethod {
	public static void main(String[] args) {
		Class<String> class1 = String.class;
		
		Method[] methods1 = class1.getDeclaredMethods();  
		for (Method method : methods1) {
			System.out.println(method);
		}
		System.out.println("------------------------------------------------");
		Method[] methods2 = class1.getMethods();  
		for (Method method : methods2) {
			System.out.println(method);
		}
		System.out.println("------------------------------------------------");
		
		try {
			Method method1 = class1.getDeclaredMethod("checkBounds",new Class[]{byte[].class,int.class,int.class});
			System.out.println(method1);
		} catch (SecurityException e) {
			e.printStackTrace();
		} catch (NoSuchMethodException e) {
			e.printStackTrace();
		}  
		System.out.println("------------------------------------------------");	
		//如果方法中的无参数，则得到方法时，只需传一个方法名即可
		try {
			//Method method2 = class1.getDeclaredMethod("hashCode");
			//getMethod只获取public的方法
			Method method2 = class1.getMethod("hashCode");
			System.out.println(method2);
		} catch (SecurityException e) {
			e.printStackTrace();
		} catch (NoSuchMethodException e) {
			e.printStackTrace();
		}  
	}
}

 

/**
 * Constructor类：同上有四种方法
 * @author Morgan
 *
 */
public class TestConstructor {
	public static void main(String[] args) {
		Class<String> class1 = String.class;
		
		Constructor<?>[] cons1 = class1.getDeclaredConstructors();  
		for (Constructor<?> constructor : cons1) {
			System.out.println(constructor);
		}
		System.out.println("------------------------------------------------");
		Constructor<?>[] cons2 = class1.getConstructors();  
		for (Constructor<?> constructor : cons2) {
			System.out.println(constructor);
		}    
		System.out.println("------------------------------------------------");
		try {
			Constructor<String> con1 = class1.getConstructor(char[].class);
			System.out.println(con1);
		} catch (SecurityException e) {
			e.printStackTrace();
		} catch (NoSuchMethodException e) {
			e.printStackTrace();
		}  
		System.out.println("------------------------------------------------");
		try {
			Constructor<String> con2 = class1.getDeclaredConstructor(new Class[]{int.class,int.class,char[].class});
			System.out.println(con2);
		} catch (SecurityException e) {
			e.printStackTrace();
		} catch (NoSuchMethodException e) {
			e.printStackTrace();
		}  
	}
}

 

 

/**
 * 由一个class得到一个类的实体
 * @author Morgan
 *
 */
public class TestGetInstance {
	public static void main(String[] args) {
		Class<String> class1 = String.class;
		try {
			//用此种方法，类必须有默认构造函数
			String obj  = (String) class1.newInstance();
			System.out.println(obj.length());
		} catch (InstantiationException e) {
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			e.printStackTrace();
		}
		
		Constructor<String> con1 = null;
		try {
			con1 = class1.getConstructor(char[].class);
		} catch (SecurityException e) {
			e.printStackTrace();
		} catch (NoSuchMethodException e) {
			e.printStackTrace();
		}
		
		try {
			String str2 =  (String) con1.newInstance(new char[]{'t','e','s','t'});
			System.out.println(str2);
		} catch (IllegalArgumentException e) {
			e.printStackTrace();
		} catch (InstantiationException e) {
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			e.printStackTrace();
		} catch (InvocationTargetException e) {
			e.printStackTrace();
		}  
	}
}

 

/**
 * method方法执行
 * @author Morgan
 *
 */
public class TestMethodInvoke {
	public static void main(String[] args) {
		String testStr = "testStr";  
		Method method = null;
		try {
			method = String.class.getMethod("charAt", new Class[]{int.class});
		} catch (SecurityException e1) {
			e1.printStackTrace();
		} catch (NoSuchMethodException e1) {
			e1.printStackTrace();
		} 
		
		try {
			Object ch = method.invoke(testStr, 1);
			System.out.println(ch);
		} catch (IllegalArgumentException e) {
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			e.printStackTrace();
		} catch (InvocationTargetException e) {
			e.printStackTrace();
		}
		
		
	}
}