Eclipse Does Not Recognize Default Method Keyword And Lambda Expression
Jun 2, 2014
I have this very annoying issue with Eclipse (I have the latest version installed). For some reason, every time I use the "default" keyword in an interface, it gives me an error similar to "Syntax error on token default", I deleted the "default" keyword, the error is gone. The same thing happens with "Lambda expression as well", say I have this object like this :
Actions myActions = () -> {System.out.print("Blah blah blah");}; ,
Eclipse also displays the error message similar to "Method body expected after (), delete '->' ". I checked the Java version I have, it is the latest one also ....
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Oct 16, 2014
I have the following structure and want to use lambda expressions with it, but an exception occurs:
class SuperClass // (package private)
public class SubClass extends SuperClass // in same package as SuperClass
I have a functional interface (a listener), which has one argument of type SubClass.
public interface MyListener() {
void myMethod(SubClass e);
}
When I use the old-school Java 7 style:
addListener(new MyListener() {
@Override
public void myMethod(SubClass e) {
System.out.println(e);
}
});
Everything works fine! If I use Java 8 lambda expression instead:
addListener(e -> {
System.out.println(e);
});
It will throw an exception:
java.lang.IllegalAccessError: tried to access class SuperClass
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Dec 7, 2014
I have an array that I filled with 30 random characters, but now I am trying to sort them in ascending order and the descending order using lambda expressions.
public class RandomCharacters {
public static void main(String args[]){
Random r =new Random();
char myarray[] = new char [30];
for (int i = 0 ; i < 30; i++)
[Code] ......
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Oct 7, 2014
What is the difference between the static keyword and transient keyword?
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Feb 7, 2014
interface I1{
void show();
void display();
default void put(){
System.out.println("I am from interface I1");
[Code] ....
This code is not working..
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Aug 27, 2014
For the below program what are the default values passed by the JVM in order to call main() method
class program
{
public static void main(String[] args)
{
System.out.println(args[0]);
System.out.println(args[1]);
}
}
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Sep 5, 2014
I am running a test servlet on Tomcat and have implemented different behaviours for the doPost and doGet methods. When I access from the browser, only the doGet method gets called ultimately.
The Firefox developer tools show me a GET request from the browser to my Tomcat instance. Do browsers ever call the POST http method? How could I make this happen?
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Feb 13, 2015
I am learning about Lambdas and am having a little difficulty in a conversion. I need to introduce a List into which the array supplied by the values method of the Field class is copied, using the asList method of the class Arrays. Then I need to convert the for loop with a forEach internal loop using a lambda expression as its parameter. The body of the lambda expression will be the code that is the present body of the for loop. I believe I have the List syntax correct ( List<String> list = Arrays.asList(data); ), but I am having a hard time on figuring out what to do with the for loop, or even where to start with it.
public AreaData(String... data) {
List<String> list = Arrays.asList(data);
/* Assert to check that the data is of the expected number of items. */
assert data.length == Field.values().length : "Incorrect number of fields";
for( Field field : Field.values() )
[Code] .....
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Jul 21, 2014
why the complier is giving the following error message "illegal start of expression" once it reach the countSpaces method.The way I see it (and I am obviously seeing it wrong), the code is public since why not, int since it returns an int # and the method has return int in it, and static I am not too sure but I get the same error message whether or not it is included
public static void main (String args[]) {
Scanner in = new Scanner(System.in);
String sentence;
System.out.println("type a sentence");
sentence = in.nextLine();
countSpaces (sentence);
[code]....
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Apr 1, 2015
I'm required to implement audit logging of all action requests. The logging should contain the action name and request parameters. I have implemented the logging in a phase listener (PhaseId.INVOKE_APPLICATION).
I'm having trouble figuring out how to get the action name from ajax requests. More specific when the form command button does not contain an action attribute:
<h:form>
<h:commandButton value="#{text.update }">
<f:ajax execute="@form" render="@form" listener="#{backing.update}" />
</h:commandButton>
</h:form>
Calling the UICommand object (which represents the pressed button) getActionExpression method returns NULL.
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Sep 7, 2014
I am very confused about why my code is not working.. The function of my code will add records in my database (MySQL), Swing components of my frame..
btnUserAdd = jButton
txtUname, txtPword, txtLname, txtFname, txtMname, txtEmpNo = jTextField
cbAccType = jComboBox
EmpNo, Uname, Pword, Lname, Fname, Mname, AccType = MySQL fields
I created a method to be called when btnUserAdd is clicked. here is the code for the method:
public void UserAdd(){
String sql = "SELECT * FROM User WHERE Uname = ? and EmpNo = ?";
try {
pst = conn.prepareStatement(sql);
[Code] ....
the error is that it does not add the record it will display JAVA.LANG.NULLPOINTEREXCEPTION...
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Jan 9, 2014
my IDE doesn't seem to recognize that my program is a Swing app.I get the following error message when I run the app: "jtabledemo.JTableDemo class wasn't found in JTableDemo project."It compiles successfully though.Here is the code verbatim:
package jtableDemo;
// Demonstrate JTable.
import java.awt.*;
import javax.swing.*;
/*
<applet code="JTableDemo" width=400 height=200>
[code]....
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Mar 19, 2014
When our applet loads on our HTTPS website, the JRE is rejecting the website certificate, saying it does not recognize the Certificate Authority (which is Thawte). Internet Explorer is happy with the certificate.
With tracing turned on, I can verify the JRE is checking the certificate authorities of IE, but for some reason rejects all of them. The trace shows this:
security: Certificate has failed the verification with the Internet Explorer ROOT certificates
security: Invalid certificate from HTTPS server
We've tested several versions of JRE 7 and the latest version of JRE 8. All of them reject the certificate authority. This happens on various versions of Windows and Internet Explorer.
Please note that I'm not referring to the certificate used to sign the applet. The JRE is happy with that certificate.
What can I do to further investigate this issue?
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Apr 26, 2015
I am almost finished with my code. The only hangup I am having is that in my client class, I can't get the total price to recognize a surcharge.
This is my output:
-------------------------------------------------
Your order consists of:
coffee, type mocha, size large, cost: $5.8
tea, flavor earl grey, size medium, cost: $3.6
The total cost of your order is: $8.4
----------------------------------------------------
Notice that the total should be $9.4, rather than $8.4. It is odd because I was able to add a surcharge to my coffee(50 cents), and it does in fact recognize it when calculating the price of the coffee. So why won't my totalPrice in the client class recognize it?
Here is my Client class:
public class CoffeeShop {
public static void main(String[] args)
//One coffee
Coffee coffee = new Coffee(16,"mocha");
coffee.set_price_per_oz(coffee.size);
[Code] ....
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Feb 14, 2014
Suppose I have
class A {
public void speak() {
System.out.println("I am class A");
}
}
class B extends A{
public void speak() {
System.out.println("I am class B");
}
}
class C extends B{
public void speak() {
System.out.println("I am class C");
}
}
Why this doesn't work while A is a super type of B ?
public static void insertElements(List<? super B> list){
list.add(new A()); //not OK, why?
}
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Feb 22, 2015
Why java uses the keyword extends when setting the bound of a type parameter(Generic) to an interface. I think using the keyword implements is more intuitive.
public static <T extends Comparable<T>>
why use extends? and not implements.
int countGreaterThan(T[] anArray, T elem) {
int count = 0;
for (T e : anArray)
if (e.compareTo(elem) > 0)
++count;
return count;
}
I know if I want to set multiple bounds I will use extends keyword, and I will concatenate the bounds using & operator.
Is this a design decision to always use extends keyword to set bounds?
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Jun 14, 2014
I've come across something that i'm not overall sure about regarding the static keyword in Java.I'm making a vertical scrolling game where the player simply shoots enemies and they shoot back as they fall, dropping items if they die such as power ups and coins. I have an enemy called Bat and this is the bullet creation code in the update method:
if(oldPlayerY + 220 > posY && getBulletDelay > 0.90f){
batBullets.add(new Bullet(posX + 10, posY - 10));
getBulletDelay = 0;
}
The method is creating a new bullet object and it then adds that to the arraylist called batBullets, which is simple enough. I then need to access this arraylist in the main game update class so I can render those bullets on the screen, even if the bat dies. I was always taught that you use the static keyword when you need to access something from the class that doesn't require an object. Because of this, I have the following code.
for(Bullet bullet : Bat.batBullets){
bullet.setY(bullet.getY - 5); // Set the bullet to fall
renderMap.getSpriteBatch().draw(bullet.batBullet(), bullet.getX(), bullet.getY()); // render the bullets
}
This seems perfectly fine to me because I need to access the batBullet arraylist and it doesn't make sense to create a new bat object as I already have random spawning in place for them.
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Dec 2, 2014
I am attaching a document which shows the current state of my registry.What I want to know is if I can [safely] delete the JavaSoft folder with all lower subfolders, then re-install jdk1.6/0_31 which, I am told, is the current version being used here by developers.According to others on the development team (not my team), there COULD be something in the registry that is preventing both the installation of java jdk AND its uninstallation.Since I cannot seem to attach any kind of document.
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Jul 22, 2014
I am trying to execute a program from the command prompt. I type java -jar zuul.jar (zuul is the name of my project) and I get a message that java is not recognized as an internal or external command. What do I do wrong?
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May 23, 2014
I need creating a java keyword program that can encipher and decipher a message using the provided keyword.
The keyword is :javbean
I have attached the message text as well...
public class Caesarcipher
{
public static final String ALPHABET = "abcdefghijklmnopqrstuvwxyz";
public static void main(String[] args)
{
String theKey = "JAVBEANDEFGHIJKLMNOPQRSTUVWXYZ";
String text= "message.txt";
[Code] ....
message.txt (763bytes)
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Jul 9, 2014
The super keyword when used explicitly in a subclass constructor must be the first statement but what about if i have a this(parameters) statements ? As the this one must also be the first statement... Does this means that i can have only one or the other ? What about when the super constructor is not explicit (aka implicit ) , can i use the this( parameters) in the same constructor ?
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Nov 7, 2014
I've been trying for a while to get my exception output to print in a particular form to System.err.
What I'm looking for as output is
KeywordException: edu.cofc.csci221.KeywordException: **Keyword Not Found**
I'm getting
Keyword Exception: edu.cofc.csci221.KeywordException
at edu.cofc.csci221.CheckLine.checkForInvalidKeyword(CheckLine.java:101)
at edu.cofc.csci221.ReadLogFile.main(ReadLogFile.java:47)
The code:
line = scan.nextLine();
try { check.checkForInvalidSymbols(line); } catch (SymbolException sEx) { System.err.print("Symbol Exception: "); sEx.printStackTrace(); }
try { check.checkForInvalidKeyword(line); }catch (KeywordException kEx) { System.err.print("Keyword Exception: "); kEx.printStackTrace(); }
if(check.checkFirstKeyword(line) && line.split(" ")[0].equals(keywords[0])) { System.out.println(line); }
[Code] ....
I'm just unsure of where to go/what to do.
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Dec 8, 2014
i need to write a method, that passes in an arraylist and a keyword,and display the name of all the people in the arrayList whose name contain the keyword (irrespective of uppercase or lowercase). how to write such a method ??
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Jan 3, 2015
//constructor
class Base
{
Base(int a) {
System.out.println("in base"+a);;
}
}
class Cons extends Base
[Code] .....
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Feb 20, 2015
How does the keyword this in the CoffeeSize class refer to the size of the coffee ? I am also confused as to how the CoffeeSize constructor comes into play to determine the cost.
public class Test
{
public static void orderCoffee(CoffeeSize size)
{
size.print();
}
public static void main(String[] args)
{
orderCoffee(CoffeeSize.SMALL);
}
[code]....
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Mar 7, 2014
I have a simple classes here one is interface and another one is abstract class when i try to compile them abstract class is givving compilation error.
public interface MyInterface{
public void getName();
public void getName(String s);
}
public class HelloWorld{}
abstract class SampleClass{
[code]....
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