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This problem is from Question 3.5 in Cracking the Coding Interview 5th Edition. The solutions was like this:
public class MyQueue<T> {
Stack<T> stackNewest, stackOldest;
......
}
So what does two < T > here mean? I searched a lot of pages and didn't get answer. Thanks.
It is the parametrization. It makes use of Java Generics to produce parametrized Classes. In your case, the class MyQueue<T> has parametrization 'T' and inside the class the Stack<T> data structure too has been parametrized with 'T'.
If you are not aware of Generics, I would suggest this article given in the documentation.
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I have one existing Java 7 method which accepts nothing but return class instance. I want to change it in java 8 using any existing functional interface but don't know what i can use here.
public NotificationPage infraSelection() {
......
return this;
}
Here NotificationPage is class name.
Maybe you can use the Supplier<T> interface?
It declares the method T get().
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I'm aware that all wrapper classes, such as String, Integer etc implements Comparable interface. Are there any classes which implements Comparator?
A glance at Javadoc (All Known Implementing Classes part) shows that it's implemented by:
Collator
RuleBasedCollator
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I want all my other objects to be able to call one common method. What should my shared method type signature for parameters look like?
public class appSocket{
public appSocket appSocket(TYPE genericInstance){
// Do something with genericInstance here
}
}
In other words, what should "TYPE" look like?
I think you're a bit confused. This just corresponds to the current object. There is no reason to ever say someObject.this.foo(). You'd just say someObject.foo(). You just pass in the object.
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i came across to a java code with like this
public class TestClass{
private static volatile TestClass instance = null;
///...............
}
What is the use of instance and volotile in java, and i don't know why do we need to explicitly give null value to class.
This variable is meant to be used in a threadpool.
here is the definition of the volatile keyword:
http://www.javamex.com/tutorials/synchronization_volatile.shtml
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In this book that I'm using to brush up, there's a relationship between generic methods and the static keyword. It appears that generic methods require that keyword, but I don't see why it's required?
Here's what the book did:
static <T> void myFunction(T [] myArray) {
//......
}
There is no requirement that generic methods be static. See Section 8.4.4 of the Java Language Specification for details (including links to other relevant parts of the spec). At the same time, there's nothing wrong with a generic method being static (or vice versa), either. It all depends on the design requirements.