Note that the wording in the JLS of that particular section has changed significantly since then. It now (JLS 11) reads: 15.9.5. Anonymous Class Declarations: An anonymous class is never final (ยง8.1.1.2). The fact that an anonymous class is not final is relevant in casting, in particular the narrowing reference conversion allowed for the cast … Read more
Joshua Bloch writes in his book Effective Java, 2nd Edition, Item 74: Inner classes should not implement Serializable. They use compiler-generated synthetic fields to store references to enclosing instances and to store values of local variables from enclosing scopes. How these fields correspond to the class definition is unspecified, as are the names of anonymous … Read more
As of JDK 18, no. JDK 18 omits enclosing instance fields from inner classes that don’t use it. However, prior to JDK 18, yes, instances of anonymous inner classes hold on to a reference to their enclosing instances even if these references are never actually used. For example, this code: public class Outer { public … Read more
Good question. Answer is No. You cannot directly call date.someMethod(); Let’s understand first what is this. Date date = new Date() { … }; Above is anonymous(have no name) sub-class which is extending Date class. When you see the code like, Runnable r = new Runnable() { public void run() { } }; It means … Read more
Java doesn’t know that doWork is going to be synchronous and that the stack frame that result is in will still be there. You need to alter something that isn’t in the stack. I think this would work final Long[] result = new Long[1]; and then result[0] = st.getLong(4); in execute(). At the end, you … Read more
Container.this.select();
Anonymous classes must extend or implement something, like any other Java class, even if it’s just java.lang.Object. For example: Runnable r = new Runnable() { public void run() { … } }; Here, r is an object of an anonymous class which implements Runnable. An anonymous class can extend another class using the same syntax: … Read more
I’m using polygenelubricants’s smaller snippet. Remember there’s no concept of nested classes in the bytecode; the bytecode is, however, aware of access modifiers. The problem the compiler is trying to circumvent here is that the method instantiate() needs to create a new instance of PrivateInnerClass. However, OuterClass does not have access to PrivateInnerClass‘s constructor (OuterClass$PrivateInnerClass … Read more
Yes, by adding an initializer method that returns ‘this’, and immediately calling that method: int myVariable = 1; myButton.addActionListener(new ActionListener() { private int anonVar; public void actionPerformed(ActionEvent e) { // How would one access myVariable here? // It’s now here: System.out.println(“Initialized with value: ” + anonVar); } private ActionListener init(int var){ anonVar = var; return … Read more
What you are seeing here is an anonymous inner class: Given the following interface: interface Inter { public String getString(); } You can create something like an instance of it like so: Inter instance = new Inter() { @Override public String getString() { return “HI”; } }; Now, you have an instance of the interface … Read more