final

Why won't declaring an array final make it immutable in Java? Doesn't declaring something final mean it can't be changed? From question related to immutable array it's clear that declaring an array final doesn't make it unchangeable. The following is possible. final int[] array = new int[] {0, 1, 2, 3}; array[0] = 42; My question is: What is the function of declaring final here then? final is only about the reference that is marked by it; there is no such thing as an immutable array in Java. When you say private final int[] xs = new int[20]; you won't be allowed to say xs = new int[10]; later

Please help me understand the difference between constant variables and final variables in Java. I am a bit confused with it. Luigi Cortese Constant is the concept, the property of the variable. final is the java keyword to declare a constant variable. As other people pointed out, from a semantic/linguistic point of view the expression constant variable is an oxymoron and, as such, we could argue about its correctness. Quoting the specification , anyway, we can read A variable of primitive type [...], that is final and initialized with a compile-time constant expression (§15.28), is called a

I got two errors after I compiled my code. The errors are: 1. local variable input is accessed within inner class; needs to be declared final String name = input.getText(); 2. local variable c_age is accessed within inner class; needs to be declared final Object child_age = c_age.getSelectedItem(); This is my code: import javax.swing.*; import java.awt.event.*; public class GUI { public static void main(String[] args) { JFrame frame = new JFrame("Try GUI"); JLabel l1 = new JLabel("Please Enter Your Child's Name"); JTextField input = new JTextField("",10); JLabel l2 = new JLabel("Choose Your

Class can be accessed from many threads. Must be logger in this case also be final and static? Thanks. All major java logging packages ( java.util.logging , log4j , etc.) are synchronized and thread safe. The standard pattern of a private final static logger per class is fine even if the class is called from multiple threads. Yes the logger should be static and final. Also preferably private. There needs be only one logger instance per class and also unless you are going to change the log preference dynamically, it is better to make it final. Logger are thread safe and you do not have to worry

This question already has answers here : In Java, what purpose do the keywords `final`, `finally` and `finalize` fulfil? (6 answers) Often these keywords confuse me. Can any one tell me exactly what the difference between them is? final keyword class On a class it means you forbid to have a child class extending yours. public final class finalClass Attribute/Field final MyObject value = new MyObject() means you won't be able to modify the instance of the object. value = xxxx won't be allowed, but you still can modify the object itself value.field = "xxx"; Method When you use final on a method,

ratingS = new JSlider(1, 5, 3); ratingS.setMajorTickSpacing(1); ratingS.setPaintLabels(true); int vote; class SliderMoved implements ChangeListener { public void stateChanged(ChangeEvent e) { vote = ratingS.getValue(); } } ratingS.addChangeListener(new SliderMoved()); If i write the above code Eclipse tells me this: Cannot refer to a non-final variable vote inside an inner class defined in a different method But if i add final before int vote it gives me this error: The final local variable vote cannot be assigned, since it is defined in an enclosing type So, how to solve? Well, the standard

We know that only final local variables can be accessed in an anonymous class, and there is a good reason here: Why are only final variables accessible in anonymous class? . However, I found that an anonymous class can still access a non-final variable if the variable is an member field of the enclosing class: How can I access enclosing class instance variables from inside the anonymous class? I am confused. We ensure that only a final local variable can be accessed in anonymous class because we don't want that the variable should be out-of-sync between anonymous class and local function. The