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