import java.lang.reflect.Field;
import java.util.List;public class FieldSpy<T> {public boolean[][] b = {{ false, false }, { true, true } };public String name  = "Alice";public List<Integer> list;public T val;public static void main(String... args) {try {Class<?> c = Class.forName(args[0]);Field f = c.getField(args[1]);System.out.format("Type: %s%n", f.getType());System.out.format("GenericType: %s%n", f.getGenericType());// production code should handle these exceptions more gracefully} catch (ClassNotFoundException x) {x.printStackTrace();} catch (NoSuchFieldException x) {x.printStackTrace();}}
}

$ java FieldSpy FieldSpy b
Type: class [[Z
GenericType: class [[Z
$ java FieldSpy FieldSpy name
Type: class java.lang.String
GenericType: class java.lang.String
$ java FieldSpy FieldSpy list
Type: interface java.util.List
GenericType: java.util.List<java.lang.Integer>
$ java FieldSpy FieldSpy val
Type: class java.lang.Object
GenericType: T

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 presentif ((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;}
}

$ java FieldModifierSpy FieldModifierSpy volatile
Fields in Class 'FieldModifierSpy' containing modifiers:  volatile
share    [ synthetic=false enum_constant=false ]$ java FieldModifierSpy Spy public
Fields in Class 'Spy' containing modifiers:  public
BLACK    [ synthetic=false enum_constant=true  ]
WHITE    [ synthetic=false enum_constant=true  ]$ java FieldModifierSpy FieldModifierSpy\$Inner final
Fields in Class 'FieldModifierSpy$Inner' containing modifiers:  final
this$0   [ synthetic=true  enum_constant=false ]$ java FieldModifierSpy Spy private static final
Fields in Class 'Spy' containing modifiers:  private static final
$VALUES  [ synthetic=true  enum_constant=false ]

import java.lang.reflect.Field;
import java.util.Arrays;
import static java.lang.System.out;enum Tweedle { DEE, DUM }public class Book {public long chapters = 0;public String[] characters = { "Alice", "White Rabbit" };public Tweedle twin = Tweedle.DEE;public static void main(String... args) {Book book = new Book();String fmt = "%6S:  %-12s = %s%n";try {Class<?> c = book.getClass();Field chap = c.getDeclaredField("chapters");out.format(fmt, "before", "chapters", book.chapters);chap.setLong(book, 12);out.format(fmt, "after", "chapters", chap.getLong(book));Field chars = c.getDeclaredField("characters");out.format(fmt, "before", "characters",Arrays.asList(book.characters));String[] newChars = { "Queen", "King" };chars.set(book, newChars);out.format(fmt, "after", "characters",Arrays.asList(book.characters));Field t = c.getDeclaredField("twin");out.format(fmt, "before", "twin", book.twin);t.set(book, Tweedle.DUM);out.format(fmt, "after", "twin", t.get(book));// production code should handle these exceptions more gracefully} catch (NoSuchFieldException x) {x.printStackTrace();} catch (IllegalAccessException x) {x.printStackTrace();}}
}

$ java Book
BEFORE:  chapters     = 0AFTER:  chapters     = 12
BEFORE:  characters   = [Alice, White Rabbit]AFTER:  characters   = [Queen, King]
BEFORE:  twin         = DEEAFTER:  twin         = DUM

int x = 1;
x = 2;
x = 3;