How can I clear the Scanner buffer in Java?
You can’t explicitly clear Scanner’s buffer. Internally, it may clear the buffer after a token is read, but that’s an implementation detail outside of the porgrammers’ reach.
Java
What is method hiding in Java? Even the JavaDoc explanation is confusing
Here, Cat.foo() is said to hide Animal.foo(). Hiding does not work like overriding, because static methods are not polymorphic. So the following will happen: Calling static methods on instances rather than classes is a very bad practice, and should never be done. Compare this with instance methods, which are polymorphic and are thus overridden. The … Read more
Determine if a String is an Integer in Java [duplicate]
The most naive way would be to iterate over the String and make sure all the elements are valid digits for the given radix. This is about as efficient as it could possibly get, since you must look at each element at least once. I suppose we could micro-optimize it based on the radix, but … Read more
Reading a .txt file using Scanner class in Java
You have to put file extension here
Two dimensional array list
You would use And then when you needed to add a new “row”, you’d add the list: I’ve used this mostly when I wanted to hold references to several lists of Point in a GUI so I could draw multiple curves. It works well. For example:
How to change already compiled .class file without decompile?
I want to change .class file’s method. I installed JD Eclipse Decompiler and opened the .class file. I added some codes and save .class file. But, .class file is not changing. I don’t know how to use decompiler. And if is it possible, how to change .class file without using decompiler. I am using Ubuntu. … Read more
Information about _JAVA_OPTIONS
Can anyone explain what does Java do when _JAVA_OPTIONS Environment variable defined & when application launched on the windows machine?
How to detect EOF in Java?
It keeps running because it hasn’t encountered EOF. At end of stream: read() returns -1. read(byte[]) returns -1. read(byte[], int, int) returns -1. readLine() returns null. readXXX() for any other X throws EOFException. Scanner.hasNextXXX() returns false for any X. Scanner.nextXXX() throws NoSuchElementException for any X. Unless you’ve encountered one of these, your program hasn’t encountered … Read more
Get keys from HashMap in Java
A HashMap contains more than one key. You can use keySet() to get the set of all keys. will store 1 with key “foo” and 2 with key “bar”. To iterate over all the keys: will print “foo” and “bar”.
Which exception to throw for invalid input which is valid from client perspective
The question is is throwing illegal argument exception the right thing to do? It depends on how you want / need to “frame” this condition; i.e. is it a bug, a user input error, or something that the program is supposed to be able to deal with? If the case of two lines not intersecting … Read more