I have an instance of Class A that I want to refer to in the constructor of multiple instances of B. How can I refer to that particular instance of Class ... |
Why are constructor calls in Java allowed only once per instance? If would be useful to set multiple instance variables in one call rather than calling several setters.
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There are several different ways I can initialize complex objects (with injected dependencies and required set-up of injected members), are all seem reasonable, but have various advantages and disadvantages. I'll ... |
I'm new to JPA and using persistence in Java anyway and I have two questions I can't quite work out: I have generated tags as:
@JoinColumn(name = "UserName", referencedColumnName = "UserName")
@ManyToOne(optional = ...
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Please advise me the difference between two ways of declaration of java constructor
public class A{
private static A instance = new A();
public ...
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I'm trying to fix a bug in one of my programs which I think might be due to Hibernate figuring out how to instantiate an instance of an object without calling ... |
Does anyone know why you can reference a static method in the first line of the constructor using this() or super(), but not a non-static method?
Consider the following working:
public class TestWorking{
...
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package company;
public abstract class A {
public A(int i) {}
public abstract void func();
}
public class B extends A {
public B(int i) { ...
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Trying to get this code off the ground:
Random random = new Random();
public Particle(int mouseInputX, int mouseInputY, int[] RGBBounds){
this(mouseInputX, mouseInputY, 6, 12+ random.nextInt(10),RGBBounds);
But netbeans ... |
Why are instance variable and methods not allowed in call to super constructors or the call to overloaded constructors?
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I cannot create object for this coding. How can I access this values I want to return the msg value in this coding?
package com.my;
import org.apache.log4j.Level;
import org.apache.log4j.Logger;
import org.apache.log4j.VectorAppender;
import org.apache.log4j.spi.LoggingEvent;
import java.util.Vector;
public class ...
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Possible Duplicate:
Cannot refer to a instance method while explicitly invoking a constructor
I have been trying to do this for long time.
public class bb ...
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Ok, so this is not allowed:
public class ServiceError extends RuntimeException {
private final UUID uuid = UUID.randomUUID();
public ServiceError(...) {
...
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Consider the below code :
class abstract normal1 extends something
{
}
class outer
{
class abstract inner extends normal1
{
}
}
class General extends outer.inner ...
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Given the following code , from some reason it won't create an instance of MyVector . What might be the problem ? The problem occurs in the line of Main :
MyVector ...
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Hi, I have a very basic (looking) question. The output from the following code is : ClassA constructor10 ClassB constructor50 ClassC constructor // code begining class ClassA { ClassA(int i){ System.out.println("ClassA constructor" + i); } } class ClassB{ ClassB(int i){ System.out.println("ClassB constructor" + i); } } class ClassC extends ClassA{ static int i=10; ClassC() { super(i); System.out.println("ClassC constructor"); } ... |
Both field initializer and instance initializer blocks taken in file order are copied to the beginning of each constructor that doesn't chain to another constructor of the same class. This file (TestInstInit.java) demonstrates several cases.class InstInitSuper { int i = 0; Object fieldInit = new Object() { public boolean equals(Object o) { System.out.println("Field Initializer: " + ++i); return false; } }; ... |
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For every class X if you don't explicitly define a constructor for it (with or without parameters) the compiler will define one for you like this: "public X() { }", i.e. it's a no-argument constructor that doesn't do anything. An instance is a realization of a class, e.g. you and I are both instantiations of the class HumanBeing and have been ... |
If you mean Class.newInstance(): avoid it. hardly any pros, cons: it's not OO. If you mean a factory method: it allows you to provide the necessary implementation for the job - you could return some interface type, and thus any implementation of an object, and not just a specific one. Look at the factory pattern. The c'tor is most simple, but ... |
The original question doesn't raise a limitation of single-threading, therefore, multi-threading is a legitimate issue. "this" refers to a completed object. The compiler, hot spot and execution hardware are all free to reorder the instructions. Any method that refers to a variable that has not been set or set completely will not execute properly. This was the grist of the article ... |
This method of construction allows an object to be declared but initialised at some future point, as is often useful. There is a further performance advantage that unused objects are never initialised. The current VM always performs null pointer checks on objects before using them so there is no performance loss from performing this check. Syntax is now much cleaner and ... |
(from our assignment) "Create two instances of the MyDate class named begDate and endDate, by using the MyDate constructor after having prompted the user 3 times for each date for values of a valid month, day, and year." and here is what I have in the executable class (it isn't much because I already have an error; it says I can't ... |