回调和解析字段修饰符

一个字段的修饰符可能也现以下：
访问修饰符：public，protected，private；
管理运行时的修饰符：transient，volatile；
限制一个实例：static
禁止修改：final
注解：Annotations

如下：

import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import static java.lang.System.out;

enum Spy { BLACK , WHITE }

public class FieldModifierSpy {
    volatile int share;
    public int instance;
    class Inner {}

    public static void main(String... args) {
		try {
			    Class<?> c = Class.forName(args[0]);
			    int searchMods = 0x0;  //0
			    for (int i = 1; i < args.length; i++) {
							searchMods |= modifierFromString(args[i]);
	   			}

	    Field[] flds = c.getDeclaredFields();
	    out.format("Fields in Class '%s' containing modifiers:  %s%n",
		       c.getName(),
		       Modifier.toString(searchMods));
	    boolean found = false;
	    for (Field f : flds) {
					int foundMods = f.getModifiers();
					// Require all of the requested modifiers to be present
					if ((foundMods & searchMods) == searchMods) {
				   			 out.format("%-8s [ synthetic=%-5b enum_constant=%-5b ]%n",
					       f.getName(), f.isSynthetic(),
					       f.isEnumConstant());
				   		   found = true;
					}
	    }

	    if (!found) {
					out.format("No matching fields%n");
	    }

        // production code should handle this exception more gracefully
			} catch (ClassNotFoundException x) {
		    	x.printStackTrace();
			}
    }

    private static int modifierFromString(String s) {
				int m = 0x0;
				if ("public".equals(s))           m |= Modifier.PUBLIC;
				else if ("protected".equals(s))   m |= Modifier.PROTECTED;
				else if ("private".equals(s))     m |= Modifier.PRIVATE;
				else if ("static".equals(s))      m |= Modifier.STATIC;
				else if ("final".equals(s))       m |= Modifier.FINAL;
				else if ("transient".equals(s))   m |= Modifier.TRANSIENT;
				else if ("volatile".equals(s))    m |= Modifier.VOLATILE;
				return m;
    }
}