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Undefined arguments in return with INT

i have the code like this when i create it like this
public final class PhpArray extends AbstractMap
{
private TreeMap t;
private HashMap m;
public PhpArray() {
this.t = new TreeMap(Request.PHP_ARRAY_KEY_COMPARATOR);
this.m = null;
}
#Override
public Object put(final Object key, final Object value) {
if (this.m != null) {
return this.m.put(key, value);
}
try {
return this.t.put(key, value);
}
catch (ClassCastException e) {
this.m = new HashMap(this.t);
this.t = null;
return this.m.put(key, value);
}
}
#Override
public Set entrySet() {
if (this.t != null) {
return this.t.entrySet();
}
return this.m.entrySet();
}
public int arraySize() {
if (this.t == null) {
throw new IllegalArgumentException("The passed PHP \"array\" is not a sequence but a dictionary");
}
if (this.t.size() == 0) {
return 0;
}
return 1 + this.t.lastKey();
}
}
but when i update my project i got error in the code
return 1 + this.t.lastKey();
the error is an arguments + is undefined.. why like that ? and how to fix the problem ?

TreeMap is a generic class but in the code in your question you have used it without type parameters. This means that this line of your code:
private TreeMap t;
is essentially this:
private TreeMap<Object, Object> t;
In other words t.lastKey() returns an Object and the operator + can't be used with Object because an Object is not a number.
Perhaps you meant to call method size() rather than method lastKey()?
Perhaps this tutorial will help?

java.lang.Field equivalent in c++

I have a code that uses Field built in function in java and i could not find a way to replace it in c++ the code is shown below,
import java.lang.reflect.Field;
public class ParameterValue {
public String objectPath;
public Object objectReference;
public String fieldPath;
public String fieldPathNoCase;
public Field field;
public double value;
public ParameterValue(String path, ObjectTree tree, Field fieldInfo) {
objectPath = path;
objectReference = tree.getObject(path);
field = fieldInfo;
fieldPath = objectPath + "." + field.getName();
fieldPathNoCase = fieldPath.toLowerCase();
read();
}
public int getPrecision() {
if (field.getType().getName() == "float" || field.getType().getName() == "double")
return 2;
else
return 0;
}
public double getPrecisionMultiplier() {
return Math.pow(10, getPrecision());
}
public void read() {
String type = field.getType().getName();
try {
if (type.equals("double"))
value = field.getDouble(objectReference);
else if (type.equals("float"))
value = field.getFloat(objectReference);
else if (type.equals("int"))
value = field.getInt(objectReference);
else if (type.equals("byte"))
value = field.getByte(objectReference);
else
throw new RuntimeException();
} catch (IllegalAccessException e) {
throw new RuntimeException(e);
}
value = Math.round(value * getPrecisionMultiplier()) / getPrecisionMultiplier();
}
public void write() {
String type = field.getType().getName();
try {
if (type.equals("double"))
field.setDouble(objectReference, value);
else if (type.equals("float"))
field.setFloat(objectReference, (float)value);
else if (type.equals("int"))
field.setInt(objectReference, (int)Math.round(value));
else if (type.equals("byte"))
field.setByte(objectReference, (byte)Math.round(value));
else
throw new RuntimeException();
} catch (IllegalAccessException e) {
throw new RuntimeException(e);
}
}
public void rebind(ObjectTree tree) {
objectReference = tree.getObject(objectPath);
}
}
What i have understood from the code is that i need to find a class that can convert the value in it to Double, Float,etc. I have looked for something that can do this but i was not able to do so.
reference of the code:
https://www.programcreek.com/java-api-examples/index.php?source_dir=SecugenPlugin-master/src/sourceafis/simple/Fingerprint.java#

As per my knowledge there is no equivalent class in C++. Now for your requirement first you list out what are all a java.lang.reflect.Field class provides in java. Once you listed all the utility methods, just sort list all methods that you really requires in your C++ application. Once done you do create a C++ class with the same name and methods types and implement the logic by yourself if possible.

Refactor overriden methods, which have difference only in the middle of the body

Sometimes methods have the only difference somwhere in the middles of their bodies and it's difficult to generalize them or extract common part of code to a single method.
Question itself: How would you refactor the following implementations of interface methods to avoid duplicate code around for loop body?
interface MyInterface {
Integer myInterfaceMethod(String inputStr);
Integer myInterfaceOtherMethod(String inputStr)
}
class MyClass implements MyInterface {
public Integer myInterfaceMethod(String inputStr) {
#Override
try {
List<String> listDependingOnString = getListByString(inputStr);
Integer result = -1;
if (inputStr != null) {
result = 0;
for (String str : listDependingOnString) {
// Some different code, given just for example
result += str.length();
}
}
return result;
} catch (Exception e) {
exceptionProcessing(e);
return null;
}
}
#Override
public Integer myInterfaceOtherMethod(String inputStr) {
try {
List<String> listDependingOnString = getListByString(inputStr);
Integer result = -1;
if (inputStr != null) {
result = 0;
for (String str : listDependingOnString) {
// Some different code, given just for example
System.out.println(str);
++result;
}
}
return result;
} catch (Exception e) {
exceptionProcessing(e);
return null;
}
}
}

For this particular example, a lambda would work nicely:
private Integer computeStringFunction(String inputStr, BiFunction<Integer,String,Integer> accumulator) {
try {
List<String> listDependingOnString = getListByString(inputStr);
Integer result = -1;
if (inputStr != null) {
result = 0;
for (String str : listDependingOnString) {
result = accumulator.apply(result, str);
}
}
return result;
} catch (Exception e) {
exceptionProcessing(e);
return null;
}
public Integer myInterfaceMethod(String inputStr) {
return computeStringFunction(inputStr,
(Integer oldValue, String str) -> oldValue + str.length());
}
public Integer myInterfaceOtherMethod(String inputStr) {
return computeStringFunction(inputStr,
(Integer oldValue, String str) -> {
System.out.println(str);
return oldValue + 1;
});
}
"accumulator" here is a function that takes an integer and a string and returns another integer, and whose intent is to keep a "running total" of some sort.
BiFunction documentation
Note: not tested

The key to remove duplicate pattern in codes is to abstract the common part to one place and then find a way to pass the different part of "code pieces" as parameters to execute, for languages in which function is first class citizen(JavaScript, Python), you can always wrap the "code pieces" as functions. But it's not applicable for Java because method in Java is not a value, one way to resolve it is to define interfaces, and then pass the instance of a class which implements the interface as parameters, with lambda expression in Java 8 it can be more simpler.
Take the code in question as example, the common pattern is:
iterate the list and process each item
accumulate the result of each item and return
Then we can define two interfaces:
#FunctionalInterface
public interface ItemHandler<T, R> {
/**
* Takes input item of type T, then returns result of type R
*/
R handle(T t);
}
And another interface to accumulate the result:
#FunctionalInterface
public interface ItemResultAccumulator<T> {
T accumulate(T t1, T t2);
}
and then your code could be refactored as(I removed all exception handling and null checking code, to make the code less verbose to view):
public class MyClass implements MyInterface {
private static final ItemResultAccumulator<Integer> ADDER = (t1, t2) -> t1 + t2;
#Override
public Integer myInterfaceMethod(String inputStr) {
return processList(getListByString(inputStr), s -> s.length(), ADDER);
}
#Override
public Integer myInterfaceOtherMethod(String inputStr) {
return processList(getListByString(inputStr), s -> {
System.out.println(s);
return Integer.valueOf(1);
}, ADDER);
}
private Integer processList(List<String> list, ItemHandler<String, Integer> handler, ItemResultAccumulator<Integer> accumulator) {
Integer result = 0;
if (list != null && list.size() > 0) {
for (String item : list) {
result = accumulator.accumulate(result, handler.handle(item));
}
}
return result;
}
private List<String> getListByString(String inputStr) {
// Your logic to generate list by input
return Lists.newArrayList(inputStr.split(","));
}
}
This is a little of my thinking of this problem, hope this could be helpful:-)

Overriding value in heap java programming

I've added to my project a new data structure Heap<Integer,Integer> but the only problem I've got is that it prints me only one time the result.
If I have the input:
v=10;new(v,20);new(a,22);print(v)
at the end of execution
Heap={1->20, 2->22},
SymTable={v->1, a->2}
But what it gives me:
Heap: 1->22
SymTable: a -> 1
v -> 1
It overrides the first value.Here is the code from the controller where is the main part:
HeapAllocation crtStmt1=(HeapAllocation) crtStmt;
String varI = crtStmt1.getVarname();
Exp e = crtStmt1.getExpression();
int i=0;
Id<Object,Integer> tbl = state.getDict();
IHeap<Integer,Integer> heap1 = state.getHeap();
int value= e.eval(tbl, heap1);
heap1.put(++i, value);
if (tbl.containsKey(varI))
tbl.update(varI,i);
tbl.update(varI, i);
The problem I guess is after this line:
heap1.put(++i, value);
because for a new operation it doesn't append to the previous one, just overrides it.
Edit:
The implementation of the heap:
public class Heap<Integer,In> implements IHeap<Integer, Integer>,Serializable{
private Map<Integer, Integer> mapp;
public Heap(){
mapp = new HashMap<Integer,Integer>();
}
public void put(Integer index, Integer value){
mapp.put(index, value);
}
public void remove(Integer index){
try{
if(isEmpty())
throw new ExceptionRepo();
else
mapp.remove(index);
}catch (ExceptionRepo ex){
System.err.println("Error: Heap is empty.");
}
}
public boolean isEmpty(){
return mapp.isEmpty();
}
public Integer get(Integer index){
return mapp.get(index);
}
public boolean containsIndex(Integer index){
return mapp.containsKey(index);
}
public void update(Integer index, Integer value){
mapp.put(index, value);
}
public String toString(){
Set<Integer> all = mapp.keySet();
Object[] keysA= all.toArray();
String res="";
for(int i=0; i<mapp.size(); i++){
Integer v = mapp.get(keysA[i]);
res += keysA[i].toString() + "->" + v.toString() + "\r\n";
}
return res;
}
}
Edit2: Maybe the problem is in the eval function implementation.To be clear, I have a Exp class:
public class Exp{
public int eval(Id<Object,Integer> tbl)throws ExceptionRepo{
return 0;
}
public String toString(){
return "";
}
public int eval(Id<Object,Integer> tbl,IHeap<Integer,Integer> heap) throws ExceptionRepo{
return 0;
}
And some derived classes that extends the Exp class.I added a new method in the ConstExp class:
public class ConstExp extends Exp implements Serializable{
int number;
public int eval(Id<Object,Integer> tbl) throws ExceptionRepo{
return number;
}
public ConstExp(int n){
number = n;
}
public String toString(){
return "" + number;
}
public int eval(Id<Object,Integer> tbl,IHeap<Integer,Integer> heap) throws ExceptionRepo{
return number; //THIS IS THE NEW METHOD
}
This class should return a value..so for "v=20", after execution of the statement it puts the value 20 in the v based on this class implementation.
If it's useful this is the statement evaluation rule for the heap(that I implemented in the controller up there):
Stack1={new(var,exp)| Stmt2|...}
SymTable1
Heap1
==>
Stack2={Stmt2|...}
let be v=eval(exp,SymTable1,Heap1) in
Heap2 = Heap1 U {newfreelocation ->v}
if var exists in SymTable1 then SymTable2 = update(SymTable1,
var,newfreelocation)
else SymTable2 = add(SymTable1,var, newfreelocation)
How to resolve this?

Null Pointer Exception upon referencing variable

I am attempting to reference a variable in a method in my class and keep running into a NullPointerException. I know it is happening at the variable pbook when it is referenced from the addPerson method. Why is this happening and how could I go about fixing it?
public class Phonebook <T> {
private LinkedList<T> pbook;
public T findPerson(T person) {
for (int i = 0; i < pbook.size(); i++) {
if (pbook.get(i).equals(person)) {
return person;
}
else
{
i++;
}
}
return null;
}
public void addPerson(T person) {
pbook.addFirst(person);
}
public void deletePerson(T person) {
for (int i = 0; i < pbook.size(); i++) {
if (pbook.get(i).equals(person)) {
pbook.remove(i);
}
else
{
i++;
}
}
}
/**
* #param args
*/
public static void main(String[] args){
try{
Phonebook<Integer> sspb = new Phonebook<Integer>();
Phonebook<String> idpb = new Phonebook<String>();
sspb.addPerson(1234567890);
idpb.addPerson("Bob");
}
catch (Exception e){
e.printStackTrace();
}
}
}

You must add a constructor to instantiate your LinkedList:
public Phonebook() {
pbook = new LinkedList<T>();
}

Change:
private LinkedList<T> pbook;
To:
private LinkedList<T> pbook = new LinkedList<T>();

private LinkedList<T> pbook; You don't create a list.
Try this.
private LinkedList<T> pbook = new LinkedList<T>()

1) You can define a constructor e.g. like this.
public Phonebook(LinkedList<T> pbook){
this.pbook = pbook;
}
Then the calling code will have to set the
pbook when instantiating the Phonebook.
2) You can initialize pbook where you declare it.
private LinkedList<T> pbook = new LinkedList<T>();