Answer to your Question: No you dont have to use constructors, none of the classes shows one so youre fine with just the default constructors beeing generated while compiling. Here is what you can do based on the assumption that this pictures information is stored in a understandable format (like for example extracted from IBMs … Read more
The name reflection is used to describe code which is able to inspect other code in the same system (or itself). For example, say you have an object of an unknown type in Java, and you would like to call a ‘doSomething’ method on it if one exists. Java’s static typing system isn’t really designed … Read more
I always thought Java uses pass-by-reference. However, I’ve seen a blog post that claims that Java uses pass-by-value. I don’t think I understand the distinction they’re making. What is the explanation?
== tests for reference equality (whether they are the same object). .equals() tests for value equality (whether they are logically “equal”). Objects.equals() checks for null before calling .equals() so you don’t have to (available as of JDK7, also available in Guava). Consequently, if you want to test whether two strings have the same value you … Read more
Go to Window → Preferences → Java → Installed JREs. And see if there is an entry pointing to your JDK path, and if not, click on Edit button and put the path you configured your JAVA_HOME environment.
Use an Iterator and call remove():
This is caused when there is a class file that your code depends on and it is present at compile time but not found at runtime. Look for differences in your build time and runtime classpaths.
The java <class-name> command syntax First of all, you need to understand the correct way to launch a program using the java (or javaw) command. The normal syntax1 is this: where <option> is a command line option (starting with a “-” character), <class-name> is a fully qualified Java class name, and <arg> is an arbitrary … Read more
Just use the appropriate method: String#split(). Note that this takes a regular expression, so remember to escape special characters if necessary. there are 12 characters with special meanings: the backslash \, the caret ^, the dollar sign $, the period or dot ., the vertical bar or pipe symbol |, the question mark ?, the … Read more
This is the problem Since a is null, NullPointerException will arise every time you use it until you initialize it. So this: will fail. A possible solution would be initialize it when declaring it: IMO more important than solving this exception, is the fact that you should learn to read the stacktrace and understand what … Read more