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General Java Questions I
} else {
System.out.println("r < s");
}
Answer1: Yes, char is indeed a 16-bit value. However, the actual answer is in the
Java
Language Specification, section 5.6.2, which is at the following URL:
http://java.sun.com/docs/books/jls/second_edition/html/conversions.doc.html#170983
In summary, the char is automagically promoted to a double. No explicit cast is
necessary since the language rules say that it gets "promoted" to a double
by John O'Conner
Q: == and equals ()... These two still make me confuse a lot of time.
Can somebody give me some thumb rule or explain it to me?
Answer: When you use == with a primitive -int, double, char, ... you are checking that
the values are identical. But if you use == with an object, you are checking that the 2
objects are stored at the same address. In other words the references pointing to the
same object...
Method equals () is different.
It is the same as ==, if it isn't overriden by the object class.
Many classes override the method equals (). In this case this method will check that
content of the object is the same or not, not addresses.
Q: Why do I get message like “wrong magic number” when I am trying to run
applet? What is magic number?
Answer: The first thing a JVM does when it loads a class is check that the first four
bytes are (in hex) CA FE BA BE. This is the "magic number" and thats why you are
getting that error, you are trying to load a file that isnt a class and so the class loader
in the JVM is throwing out that exception.
Make sure you transfer the class files to site in binary mode, rather than text or ASCII
mode.
An error from the browser saying "cannot start applet ... bad magic number" usually
means that one of the class files on the server is corrupted. '
Replace your class binary files on the web server; clean up the cache of your
browser, and reload your applet.
Q: In java, I found a lot of methods, which let you enter a line (read (), readLine ()
e.c.t). They all wait until return is pressed, and then start providing you the
information.
Does anyone know if there is a read method available whit the desired behaviour, i.e.
which doesn't wait for return being pressed?
Answer: Java does not provide it, the terminal itself waits until return is pressed
before sending the entered line to Java.
You need to use some platform specific mechanism to change the terminal settings.
Q: Can I pass a function as a parameter in Java? If so, how?
Answer: No, you cannot. But you can pass an object with method and then just use
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