Develop Reference

values of a object stored in a linked list printing but not useable

I am fairly new to java and working on a project to simulate a CPU scheduler in Java and i am using a linked list to store each process object that is read in from a external master list. When I test print the processes and the variables they contain, everything comes out as expected but whenever I try and do something with them it stops working.
public class process
String ID;
int Arrive;
int ExecSize;
int Execstore;
int Tstart;
int Tend;
int quant;
public process(String ID,int Arrive,int ExecSize) {
this.ID = ID;
this.Arrive = Arrive;
this.ExecSize = ExecSize;
this.Execstore=ExecSize;
this.Tend = 0;
this.Tstart = 0;
this.quant = 4;
}
public void setquant(int update) {
this.quant = update;
}
public int getquant() {
return quant;
}
public void setExecSize(int update) {
this.ExecSize = update;
}
public void setTend(int update) {
this.Tend = update;
}
public void setTstart(int update) {
this.Tstart = update;
}
String getID() {
return ID;
}
int getArrive() {
return Arrive;
}
int getExecSize() {
return ExecSize;
}
int getTstart() {
return Tstart;
}
int getTend() {
return Tend;
}
int getExecstore() {
return Execstore;
}
and this is the class used for the simulation
public class fcfs {
int disp;
int Ttotal = 0;
int Exec;
int Turn;
int Wait;
String output;
LinkedList<process> Que = new LinkedList<process>();
LinkedList<process> Quecleared = new LinkedList<process>();
public fcfs(LinkedList<process> B,int D) {
Que.addAll(B);
disp=D;
}
public void run()
{
while (Que != null)
{
Ttotal = Ttotal + disp;
System.out.println(Que.getFirst().getExecSize());
Exec=Que.getFirst().getExecSize();
output += String.format("T%d: %s\n",Ttotal,Que.getFirst().getID());
Que.getFirst().setTstart(Ttotal);
Ttotal = Ttotal+Exec;
Que.getFirst().setTend(Ttotal);
Quecleared.add(Que.poll());
}
}
So whenever i use System.out.println I get the expected result that I read into the list. But anything else I try to do in reference to elements of the process object will not work. Any help would be greatly appreciated

while (!Que.isEmpty())
{
Ttotal = Ttotal + disp;
System.out.println(Que.peekFirst().getExecSize());
Exec=Que.peekFirst().getExecSize();
output += String.format("T%d: %s\n",Ttotal,Que.peekFirst().getID());
Que.peekFirst().setTstart(Ttotal);
Ttotal = Ttotal+Exec;
Que.peekFirst().setTend(Ttotal);
Quecleared.add(Que.pollFirst());
}
This shouldn't throw an error on Exec = Que.peekFirst().getExecSize();
That error is thrown when your container is empty.
EDIT
In your code you specified the condition Que != null. In java once an object has been instantiated it is no longer considered null even if it IS empty. Most likely what was happening here is you continued iterating through your while(Que != null) loop until you had called Que.poll() on all elements of the list.
After clearing the list you did not exit the loop because Que still was not null. Then calling getFirst() on the empty instance of a LinkedList threw an exception.
A similar situation can be seen here with null vs empty strings:
Difference between null and empty ("") Java String
EDIT 2
It also appears that your class methods for getID(), getExecSize(), etc are passing values by reference as opposed to copying their value. Thus any change you make after passing the reference from queue will alter any copies you tried to make of it.
This can be best avoided by creating a new instance of an object and returning that from your function. Shown in an answer on the question linked below:
class Foo {
private Bar myBar;
public Foo deepCopy() {
Foo newFoo = new Foo();
newFoo.myBar = myBar.clone(); //or new Bar(myBar) or myBar.deepCopy or ...
return newFoo;
}
}
For more information on ways to pass values as opposed to reference values of your pre-existing instances, as well as what a shallow copy actually is, check this link: In Java, what is a shallow copy?

Java Array of InnerClass throwing java.lang.NoSuchFieldError

I am trying to brushup java after a long time.
Any help is much appreciated.
For demonstration I have Animal Class that has an array of innerclass of Organs.
public class Animal
{
String nameOfAnimal;
Organs [] vitalOrgans = new Organs[3];
public Animal()
{
}
public String getNameOfAnimal() {
return nameOfAnimal;
}
public void setNameOfAnimal(String nameOfAnimal) {
this.nameOfAnimal = nameOfAnimal;
}
#Override
public String toString() {
return "Animal{" + "nameOfAnimal=" + nameOfAnimal + "}";
}
class Organs{
String nameOfOrgan;
public String getNameOfOrgan() {
return nameOfOrgan;
}
public void setNameOfOrgan(String nameOfOrgan) {
this.nameOfOrgan = nameOfOrgan;
}
#Override
public String toString() {
return "Organs{" + "nameOfOrgan=" + nameOfOrgan + '}';
}
}
}
Now in driver file when I make call there is no syntactical error but I get "Exception in thread "main" java.lang.NoSuchFieldError: vitalOrgans"
Animal mamal = new Animal();
mamal.setNameOfAnimal("Chimp");
mamal.vitalOrgans[0].setNameOfOrgan("Heart");
System.out.println(mamal.vitalOrgans[0].getNameOfOrgan());
What would be the way to make this (or similar idea) to work.
Thanks.

You would need to initialize the vitalOrgrans with new Organs(). Like:
public Animal() {
for (int i = 0; i < vitalOrgans.length; i++) {
vitalOrgans[i] = new Organs();
}
}
Because when you say :
Organs[] vitalOrgans = new Organs[3];
You are creating an array of 3 null Organs. Hence the null pointer exception, when accessing "vitalOrgans[i].".

Taking the relevant bit of code:
public class Animal
{
//...
Organs [] vitalOrgans = new Organs[3];
//...
}
Since your declaration of vitalOrgans was never given an access modifier (i.e. one of private, public, protected) it took on default access, which means only other classes in the same package can see it. Since your other block of code is not in the same package, it cannot see the field.
A minimally viable modification to just make it work would be to set the access to public:
public class Animal
{
//...
public Organs [] vitalOrgans = new Organs[3];
//...
}
While this works, it's not necessarily the best solution, as if you ever change how vitalOrgans is represented, or need to perform any validation, those edits would have to be done throughout the application. Thus, a better solution (and also, a major stylistic convention in Java for those exact reasons) is to make it (and all your fields, in fact) private and access via methods:
public class Animal {
private String nameOfAnimal;
private Organs[] vitalOrgans = new Organs[3];
//...
public Organs[] getVitalOrgans() {
return vitalOrgans;
}
//Alternative accessor that fetches only one organ.
public Organs getVitalOrgan(int index) {
if(index >= 0 && index < vitalOrgans.length)
return vitalOrgans[index];
else
return null;
}
public void setVitalOrgans(Organs[] vitalOrgans) {
this.vitalOrgans = vitalOrgans
}
//...
}
Your caller could then access Organs via either form of the get method (note, you probably want Organs to be public):
Animal.Organs futureMammalHeart = mamal.getVitalOrgan(0); //Animal.Organs due to Organs being an inner class.
if(futureMammalHeart != null) //Demonstration of null check. Safety first!
futureMammalHeart.setNameOfOrgan("Heart");
Animal.Organs[] mammalianVitalOrgans = mamal.getVitalOrgans();
if(mammalianVitalOrgans != null) //Just in case...
System.out.println(mamal.mammalianVitalOrgans[0].getNameOfOrgan());
Also, as Ari mentioned in his answer, don't forget to initialize the organs in your array, otherwise you will get a NullPointerException!

Creating array of methods returning boolean and iterating through for-each loop

Okay so I have a batch of methods returning boolean values of true/false.
private void saveChangesOnEditButtonActionPerformed(java.awt.event.ActionEvent evt) {
updateMainTabsAccess();
updateUserPaymentTabPermissions();
updateUserRegistrationTabPermissions();
updateUserStudentsTabPermissions();
updateUserFacultyTabPermissions();
updateUserHomePermissions(); //saves any update made on existing user settings/permissions
updateUserInformation(); // sasve any update made on existing user information such as username
}
I would like to know if it's possible for me to check each of the methods' return value through a for-each loop.
I'm thinking of creating a private boolean isUpdateSuccessful() method.
Say like,
private boolean isUpdateSuccessful(){
Boolean a = updateMainTabsAccess();
Boolean b = updateUserPaymentTabPermissions();
//........so on....
Boolean result = (a && b &&...)
return result;
}
Problem is, I don't know if it's possible to put them in an arraylist or component array like
ArrayList<Boolean> listOfMethods = new ArrayList<Boolean>(method1,method2..);
So that I can then check each through a for-each loop
for(Boolean b:listOfMethods){
Boolean successful=true;
successful = (successful && b)
}
My questions are:
1.) How do I extract the return values of these methods and use the methods to initialize the Arraylist.
2.) Using for-each loop, is there any possibility of what I'm trying to do? I none, then what do you suggest I do?
I'd appreciate any answer or suggestion. I simply want to check if every method was successful. I thought of using ?1:0:
Thanks in advance.

If I am you, I would do this. Just a sample code:
private void saveChangesOnEditButtonActionPerformed(java.awt.event.ActionEvent evt) {
if (updateMainTabsAccess()) {
if (updateUserPaymentTabPermissions()) {
if (updateUserRegistrationTabPermissions()) {
...
} else {
// error on update registration
}
} else {
// error on update payment
}
}
With the above style:
You don't execute other methods when the before one fails.
Can have detailed error messages for each error.
You need not to main a collection and iteration.

Why not use a Stream to check the results:
Stream.<Boolean>of(updateMainTabsAccess(),
updateUserPaymentTabPermissions(),
updateUserRegistrationTabPermissions(),
updateUserStudentsTabPermissions(),
updateUserFacultyTabPermissions(),
updateUserHomePermissions(),
updateUserInformation()).allMatch(b -> b);
this way you get rid of short circuit evaluation and also don't need to create method references for each method.
method references
List<Supplier<Boolean>> methods = Arrays.asList(this::updateMainTabsAccess,
this::updateUserPaymentTabPermissions,
...
);
for (Supplier<Boolean> supplier : methods) {
boolean methodResult = supplier.get();
...
}
This can hardly be considered an improvement though...

this will find all method in side your class which is return Boolean after automatically invoke method one by one and store response to successful variable
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.List;
public class Test {
public static void main(String[] args) {
Test test = new Test();
Class c = test.getClass();
boolean successful = true;
for (Method method : c.getDeclaredMethods()) {
if (method.getReturnType().toString().equals("boolean")) {
try {
String mname = method.getName();
Object o = method.invoke(test, null);
System.out.format("%s() returned %b%n", mname, (Boolean) o);
successful = successful && (Boolean) o;
} catch (Exception e) {
e.printStackTrace();
}
}
}
System.out.println("final answer : " + successful);
}
public boolean a() {
return true;
}
public boolean b() {
return false;
}
public boolean c() {
return false;
}
}
Hope its help to you.

If you want every method to be executed and check if every method scucceded you could simply write
boolean success = updateMainTabsAccess() &
updateUserPaymentTabPermissions() &
updateUserRegistrationTabPermissions() &
updateUserStudentsTabPermissions() &
updateUserFacultyTabPermissions() &
updateUserHomePermissions() &
updateUserInformation();

You have already received some answers.
Fabian's is a good one if you are using java 8.
But to answer directly your points
1.) How do I extract the return values of these methods and use the methods to initialize the Arraylist.
ArrayList<Boolean> resultsList = new ArrayList<Boolean>();
resultsList.add(updateMainTabsAccess());
...
2.) Using for-each loop, is there any possibility of what I'm trying to do? I none, then what do you suggest I do?
boolean res = true;
for (Boolean singleResult : resultsList) {
res = res && singleResult;
}

Here is the old style way to acheive your goal when Lambdas weren't introduced by Java 8.
public class TestMethodsListCall {
public abstract class Checker {
public abstract boolean check();
}
public static void main(String[] args) {
new TestMethodsListCall();
}
public TestMethodsListCall() {
final TestMethodsListCall that = this;
List<Checker> checkers = Arrays.asList( //
new Checker() { public boolean check() { return that.methodA(); } }, //
new Checker() { public boolean check() { return that.methodB(); } } //
// , ...
);
boolean res = true;
for (Checker c : checkers) {
res = res & c.check();
if (!res) {
// Break, display some message or all together
}
}
}
public boolean methodA() {
return true;
}
public boolean methodB() {
return false;
}
}

EasyMock: How to Verify Method Order for Set of Values Where Order of Set Does Not Matter

I have a test in which I have a set of specific values for which two different methods will execute once for each value in the set. I need to check that the two methods are called in a specific order in relation to each other, but not in relation to the order of the set of values. For example:
String[] values = { "A", "B", "C" };
for (...<loop over values...) {
methodOne(value);
methodTwo(value);
}
It does not matter which order values is in, but I need to verify that methodOne() and methodTwo() are called for each value in the set AND that methodOne() is always called before methodTwo().
I know that I can create a control and expect methodOne() and methodTwo() for each value, then do control.verify(), but this depends on values being in a specific order.
Is there an elegant way to do this?
Thanks

You can do this using andAnswer().
Basically, inside the andAnswer() from methodOne() you set some variable to hold what the passed in value was.
Then in the andAnswer() for methodTwo() you assert that the same argument matches what you saved from your methodOne answer.
Since each call to methodOne will modify this variable it will make sure methodTwo() is always called after methodOne().
Note this solution is not thread safe
First you need something to hold the variable from the methodOne call. This can be a simple class with a single field or even an array of one element. You need this wrapper object because you need to reference it in the IAnswer which requires a final or effectively final field.
private class CurrentValue{
private String methodOneArg;
}
Now your expectations. Here I called the class that you are testing (The System Under Test) sut:
String[] values = new String[]{"A", "B", "C"};
final CurrentValue currentValue = new CurrentValue();
sut.methodOne(isA(String.class));
expectLastCall().andAnswer(new IAnswer<Void>() {
#Override
public Void answer() throws Throwable {
//save the parameter passed in to our holder object
currentValue.methodOneArg =(String) EasyMock.getCurrentArguments()[0];
return null;
}
}).times(values.length); // do this once for every element in values
sut.methodTwo(isA(String.class));
expectLastCall().andAnswer(new IAnswer<Void>() {
#Override
public Void answer() throws Throwable {
String value =(String) EasyMock.getCurrentArguments()[0];
//check to make sure the parameter matches the
//the most recent call to methodOne()
assertEquals(currentValue.methodOneArg, value);
return null;
}
}).times(values.length); // do this once for every element in values
replay(sut);
... //do your test
verify(sut);
EDIT
you are correct that if you are using EasyMock 2.4 + you can use the new Capture class to get the argument value in a cleaner way for methodOne(). However, you may still need to use the andAnswer() for methodTwo() to make sure the correct values are called in order.
Here is the same code using Capture
Capture<String> captureArg = new Capture<>();
sut.methodOne(and(capture(captureArg), isA(String.class)));
expectLastCall().times(values.length);
sut.methodTwo(isA(String.class));
expectLastCall().andAnswer(new IAnswer<Void>() {
#Override
public Void answer() throws Throwable {
String value =(String) EasyMock.getCurrentArguments()[0];
assertEquals(captureArg.getValue(), value);
return null;
}
}).times(values.length);
replay(sut);

For those interested, I solved this issue using intended EasyMock functionality. The solution was to make a custom IArgumentMatcher to verify against a collection of values and to enforce how many times each value is matched consecutively. The custom matcher, in addition to using strict mocking exactly solves the original problem.
public class SetMatcher implements IArgumentMatcher {
private List<String> valuesToMatch;
private List<String> remainingValues;
private String currentValue = null;
private int timesMatched = 0;
private int setMatches;
public SetMatcher(final List<String> valuesToMatch, final int times) {
this.valuesToMatch = new ArrayList<String>(valuesToMatch);
this.remainingValues = new ArrayList<String>(valuesToMatch);
this.setMatches = times;
}
public String use() {
EasyMock.reportMatcher(this);
return null;
}
public void appendTo(StringBuffer buffer) {
if (this.remainingValues.size() == 0) {
buffer.append("all values in " + this.valuesToMatch + " already matched " + this.setMatches + " time(s)");
} else {
buffer.append("match " + this.valuesToMatch + " " + this.setMatches + " time(s) each");
}
}
public boolean matches(Object other) {
if (this.timesMatched >= this.setMatches) {
this.currentValue = null;
this.timesMatched = 0;
}
if (null == this.currentValue) {
if (this.remainingValues.contains(other)) {
this.currentValue = (String) other;
this.timesMatched = 1;
this.remainingValues.remove(other);
return true;
}
} else if (this.currentValue.equals(other)) {
this.timesMatched++;
return true;
}
return false;
}
}
The class being tested:
public class DataProcessor {
private ServiceOne serviceOne;
private ServiceTwo serviceTwo;
public DataProcessor(ServiceOne serviceOne, ServiceTwo serviceTwo) {
this.serviceOne = serviceOne;
this.serviceTwo = serviceTwo;
}
public void processAll(List<String> allValues) {
List<String> copy = new ArrayList<String>(allValues);
for (String value : copy) {
this.serviceOne.preProcessData(value);
this.serviceTwo.completeTransaction(value);
}
}
}
And the test:
public class DataProcessorTest {
List<String> TEST_VALUES = Arrays.asList("One", "Two", "Three", "Four", "Five");
#Test
public void test() {
IMocksControl control = EasyMock.createStrictControl();
ServiceOne serviceOne = control.createMock(ServiceOne.class);
ServiceTwo serviceTwo = control.createMock(ServiceTwo.class);
SetMatcher matcher = new SetMatcher(TEST_VALUES, 2);
for (int i = 0; i < TEST_VALUES.size(); i++) {
serviceOne.preProcessData(matcher.use());
serviceTwo.completeTransaction(matcher.use());
}
control.replay();
DataProcessor dataProcessor = new DataProcessor(serviceOne, serviceTwo);
dataProcessor.processAll(TEST_VALUES);
control.verify();
}
}
The test will fail for any of the following:
ServiceOne and ServiceTwo are called in the wrong order
ServiceOne and ServiceTwo are not called consecutively with the same value
ServiceOne or ServiceTwo are called with a value that is not in the specified value list
A call is made beyond the number of expected times for a value in the list

How I can empty values get and set together in java?

I have get and set class :
public static class Structure{
private String YOne = null;
private String YTwo = null;
public String getYOne() {
return YOne;
}
public void setYOne(String YOne) {
this.YOne = YOne;
}
public String getYTwo() {
return YTwo;
}
public void setYTwo(String YTwo) {
this.YTwo = YTwo;
}
}
Then I fill that in my class :
Structure.setYOne("my value");
Structure.setYTwo("my value");
How I can empty all of them ?
Notice : I don't like empty that one by one .

You can implement a method in your Structure class that sets all the fields to null using Reflection:
public void clearFields() throws IllegalArgumentException, IllegalAccessException {
Field[] properties = this.getClass().getDeclaredFields();
for (Field f : properties) {
f.setAccessible(true);
f.set(this, null);
}
}

Rebuild your object, no other choice if you don't want to do it one by one
Structure s = new Structure();
// YOne and YTwo are null
s.setYOne("my value");
s.setYTwo("my value");
// YOne and YTwo are not null;
s = new Structure();
// YOne and YTwo are null again
edit : be careful though, it could mess up your reference if your object is used in another class.

You are lacking basic class and object concept here. You need to create an array of objects of Structure class. The use a foor loop to loop through all the objects and set methods.
for(Structure x : your_array_of_Structures ){
x.set(whatever);
x.get(whatever);
}
Go to http://www.tutorialspoint.com/java/java_loop_control.htm where you can get more tutorials on how to do these basic things in Java.