Mega Code Archive
BufferedReader reflection
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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();
}
}
}
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