BufferedReader reflection : Class Loader « Reflection « Java Tutorial





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import static java.lang.System.out;

import java.io.BufferedReader;
import java.io.CharArrayReader;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.lang.reflect.Field;
import java.util.Arrays;

public class GrowBufferedReader {
  private static final int srcBufSize = 10 * 1024;
  private static char[] src = new char[srcBufSize];
  static {
    src[srcBufSize - 1] = 'x';
  }
  private static CharArrayReader car = new CharArrayReader(src);

  public static void main(String... args) {
    try {
      BufferedReader br = new BufferedReader(car);

      Class<?> c = br.getClass();
      Field f = c.getDeclaredField("cb");

      // cb is a private field
      f.setAccessible(true);
      char[] cbVal = char[].class.cast(f.get(br));

      char[] newVal = Arrays.copyOf(cbVal, cbVal.length * 2);
      if (args.length > 0 && args[0].equals("grow"))
        f.set(br, newVal);

      for (int i = 0; i < srcBufSize; i++)
        br.read();

      // see if the new backing array is being used
      if (newVal[srcBufSize - 1] == src[srcBufSize - 1])
        out.format("Using new backing array, size=%d%n", newVal.length);
      else
        out.format("Using original backing array, size=%d%n", cbVal.length);

      // production code should handle these exceptions more gracefully
    } catch (FileNotFoundException x) {
      x.printStackTrace();
    } catch (NoSuchFieldException x) {
      x.printStackTrace();
    } catch (IllegalAccessException x) {
      x.printStackTrace();
    } catch (IOException x) {
      x.printStackTrace();
    }
  }
}










7.7.Class Loader
7.7.1.URL class loader
7.7.2.extends URLClassLoader
7.7.3.Load classes
7.7.4.how to use reflection to print the names and values of all nonstatic fields of an object
7.7.5.Runs a jar application from any url
7.7.6.BufferedReader reflection
7.7.7.Get the class By way of an object
7.7.8.Get the class By way of a string
7.7.9.Get the class By way of .class
7.7.10.Catch InvocationTargetException
7.7.11.Determining from Where a Class Was Loaded
7.7.12.Dynamically Reloading a Modified Class
7.7.13.Creating an Object Using a Constructor Object
7.7.14.Create an object from a string
7.7.15.Using the forName() method
7.7.16.Context ClassLoader
7.7.17.A tree structure that maps inheritance hierarchies of classes
7.7.18.Analyze ClassLoader hierarchy for any given object or class loader
7.7.19.Instantiate unknown class at runtime and call the object's methods
7.7.20.Load Class