Returns true if the specified file extension can be read : ImageIO « 2D Graphics « Java Tutorial

1. Java Tutorial
2. 2D Graphics
3. ImageIO

import java.io.File;
import java.util.Iterator;

import javax.imageio.ImageIO;

public class Main {
  public static void main(String[] argv) throws Exception {
    boolean b;

    // Check availability using a format name
    b = canReadExtension("foo"); // false
    b = canReadExtension("gif"); // true
    b = canReadExtension("giF"); // true
  }
  // Returns true if the specified file extension can be read
  public static boolean canReadExtension(String fileExt) {
    Iterator iter = ImageIO.getImageReadersBySuffix(fileExt);
    return iter.hasNext();
  }

}