vendredi 22 septembre 2017

java reflection field bitwise operation

I do have good understanding of bitwise operations. My question is case-specific. In the following code taken from oracle tutorial, is it possible to change the expression:

if ((foundMods & searchMods) == searchMods) 

To:

if (foundMods == searchMods) 

? ... because we are not extracting any flag, we are only testing for equality. Right? ... or am missing something?

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;
int instance;
class Inner {}

public static void main(String... args) {
try {
    Class<?> c = Class.forName(args[0]);
    int searchMods = 0x0;
    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;
}
}





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