Develop Reference

How to prevent the error: null > 0 java

I currently have an enumlist. The enumlist gets filled at random, so there is a possibility that one has the value null. That is logical because it doesn't get filled.
The problem is further in my code I have:
if (player.Enumlist().get(CART_BLACK) > 0) {
}
Java throws a NullPointerException. Is there something I could add to the if-statement to prevent this error?

If get(CART_BLACK) may return null:
Get the value before the condition and replace it with a negative value if it's null:
Integer cartBlack = player.Enumlist().get(CART_BLACK);
if (cartBlack == null) cartBlack = -1;
if (cartBlack > 0) {
If player.Enumlist() may return null
Similar, but not quite identical:
final Enumlist list = player.Enumlist();
final int cartBlack = list == null ? -1 : list.get(CART_BLACK);
if (cartBlack > 0) {

You'll need to guard against nullity:
if(player.Enumlist().get(CART_BLACK) != null &&
player.Enumlist().get(CART_BLACK) > 0) {...}
or a more efficient version:
Integer temp = player.Enumlist().get(CART_BLACK);
if (temp != null && temp > 0){...}

if( player.Enumlist().get(CART_BLACK) != null && player.Enumlist().get(CART_BLACK) > 0) {
}
This will work because ifs are checked from left to right, and if one condition fails the rest won't be evaluated and you won't get the NPE.

Correcting the issue at the end makes the trick but it is not fine because it means that it may occur in other invocations. Besides, as a consequence, you may finish by overusing not null guards as you will never know if the null is a normal case.
So you should favor the use of Optional (Java 8 or Guava) as return rather than null to make your API clearer (it may return an empty thing so convey that) and more robust (the contained object has to be specifically unwrapped).
For example :
Optional<Integer> optValue = player.Enumlist().get(CART_BLACK);
optValue.filter(v -> v > 0)
.ifPresent( v -> ...);

You need to do Null Checking:
if (player == null || player.Enumlist () == null) {
throw new Exception("Player or Enumlist cannot be null");
}
You should also check that the Integer value is not null, but I guess that would be pretty weird if you wrote the code.
You are using get which could give you an IndexOutOfBoundsException eventually. You could check that using the size method or using streams.
If (player.Enumlist().size() > CART_BLACK && player.Enumlist().get(CART_BLACK) != null && player.Enumlist().get(CART_BLACK) > 0) {
//...
}

You may check for Null also handle the exception using try..catch block
try
{
if( player.Enumlist().get(CART_BLACK)!=null && player.Enumlist().get(CART_BLACK) > 0)
{
}
}
catch(NullPointerException)
{
//handle exception here
}

Introduce a new variable instead of reusing the parameter "entity"

I am solving SonarQube issues , in that issues I face an below warning any one please tell me how can i fix it,
Here is my class
public static Agency updateEntity(AgencyModel model, Agency entity) {
if (model == null || entity == null) {
return null;
}
if (entity.getAgencyId() != model.getAgencyId()) {
entity = new Agency()
// for the above variable 'entity' i get the warning, "Introduce a new
variable instead of reusing the parameter "entity".
}
entity.setAgencyId(model.getAgencyId());
if (entity.getAgencyLogoLarge() == null) {
entity.setAgencyLogoLarge(new File());
}
entity.setAgencyLogoLarge(FileModel.updateEntity(model.getAgencyLogoLarge(), entity.getAgencyLogoLarge()));
if (entity.getAgencyLogoSmall() == null) {
entity.setAgencyLogoSmall(new File());
}
entity.setAgencyLogoSmall(FileModel.updateEntity(model.getAgencyLogoSmall(), entity.getAgencyLogoSmall()));
entity.setAgencyName(model.getAgencyName());
entity.setContactPersons(
AgencyContactPersonModel.updateEntities(model.getContactPersons(), entity.getContactPersons()));
entity.setOtherDetails(model.getOtherDetails());
entity.setClassification(ClassificationModel.updateEntity(model.getClassification(), entity.getClassification()));
entity.setStatus(entity.getStatus());
entity.setCreatedBy((model.getCreatedBy() != null && model.getCreatedBy() != 0) ? model.getCreatedBy()
: entity.getCreatedBy());
entity.setUpdatedBy((model.getUpdatedBy() != null && model.getUpdatedBy() != 0) ? model.getUpdatedBy()
: entity.getUpdatedBy());
entity.setUpdatedDate(new Date());
entity.setStatus(Constant.ACTIVE);
return entity;
}
In above method i get that warning , will any one please tell me that what is the best approach to solve the above problem.

Assigning a value to a method argument often indicates a bug (even though this is not the case in your example), which is probably why SonarQube gives that warning.
Assuming you have no way of disabling that warning (or you don't want to), you can eliminate it by introducing a new local variable:
public static Agency updateEntity(AgencyModel model, Agency entity) {
Entity result;
if (model == null || entity == null) {
return null;
}
if (entity.getAgencyId() != model.getAgencyId()) {
result = new Agency();
} else {
result = entity;
}
... use result variable instead of entity variable ...
return result;
}

Expressions should not be too complex for conditional operators

I am using Sonar and its giving me the suggestion "Expressions should not be too complex"
How can I make a better representation of below code?
Code
if (eDelivery != null && Boolean.parseBoolean(eDelivery.getReceiveConfirmationElectronically()) &&
!Boolean.parseBoolean(eDelivery.getInvalidEmailAddress()) && !Boolean.parseBoolean(eDelivery.getEmailUndeliverable()) &&
eDelivery.getUserEmailAddress() != null && !eDelivery.getUserEmailAddress().isEmpty()) {
// Implementation code
}

These conditions all relate to the eDelivery object, so deal with this there.
First, there's the question of why you're doing all these parseBoolean calls for properties that look like they should be boolean to start with. But okay, let's assume that you can't change that. Fine, so add 2ndary methods:
public class EDelivery {
public boolean isReceiveConfirmationElectronically() {
return Boolean.parseBoolean(getReceiveConfirmationElectronically())
}
// &etc...
Already that cleans it up considerably:
if (eDelivery != null && eDelivery.isReceiveConfirmationElectronically() &&
!eDelivery.isInvalidEmailAddress() && !eDelivery.isEmailUndeliverable() &&
eDelivery.getUserEmailAddress() != null && !eDelivery.getUserEmailAddress().isEmpty()) {
// Implementation code
But that doesn't address the number of conditions. So now:
// in EDelivery class
public boolean isEmailGood() {
return !isInvalidEmailAddress() && !isEmailUndeliverable() &&
getUserEmailAddress() != null && !getUserEmailAddress().isEmpty())
}
So now we're at:
if (eDelivery != null && eDelivery.isReceiveConfirmationElectronically() &&
eDelivery.isEmailGood()) {
// Implementation code
At this point you've met the requirement, but if you wanted to take it a little further:
// in EDelivery class
public boolean canSendElectronicConfirmation(){
return isEmailGood() && isReceiveConfirmationElectronically();
}
Which reduces your original if statement to
if (eDelivery != null && eDelivery.canSendElectronicConfirmation()) {
// Implementation code

Findbugs-NP - NP_NULL_ON_SOME_PATH

Findbugs is showing NP_NULL_ON_SOME_PATH for a line.
It says that there is a branch of statement that, if executed, guarantees that a null value will be dereferenced, which would generate a NullPointerException when the code is executed.
Of course, the problem might be that the branch or statement is infeasible and that the null pointer exception can't ever be executed; deciding that is beyond the ability of FindBugs.
Here is the code:
public int compare(Object o1, Object o2)
{
....
String sTypeName1 = row1.getFieldValue(OBJECT_TYPE_FIELD_NAME);
String sTypeName2 = row2.getFieldValue(OBJECT_TYPE_FIELD_NAME);
if (sTypeName1!= null && sTypeName1.indexOf("~") != -1)
{
sTypeName1 = m_oc.getString(sTypeName1);
}
if (sTypeName2!= null && sTypeName2.indexOf("~") != -1)
{
sTypeName2 = m_oc.getString(sTypeName2);
}
int cf = sTypeName1.compareTo(sTypeName2);
if (cf == 0)
{
cf = o1.toString().compareTo(o2.toString());
}
return cf;
}
It is showing 2 errors of same kind for the code:
int cf = sTypeName1.compareTo(sTypeName2);
Here it says that there is a possible null pointer dereference from the value loaded from sTypeName1.
So I had to put a null check before this code like:
if(sTypeName1 != null && sTypeName2 != null)
{
int cf = sTypeName1.compareTo(sTypeName2);
}
but the issue is not resolved. :(
Could anyone suggest a solution and also what is wrong with my approach?
Thanks a lot for going through my question :)

For me the issue is resolved. This code does not produce a bug report:
String sTypeName1 = row1.getFieldValue("qqq");
String sTypeName2 = row2.getFieldValue("www");
if (sTypeName1 != null && sTypeName1.indexOf("~") != -1) {
sTypeName1 = m_oc.getString(sTypeName1);
}
if (sTypeName2 != null && sTypeName2.indexOf("~") != -1) {
sTypeName2 = m_oc.getString(sTypeName2);
}
int cf = 0;
if (sTypeName1 != null && sTypeName2 != null) {
cf = sTypeName1.compareTo(sTypeName2);
}
if (cf == 0) {
cf = o1.toString().compareTo(o2.toString());
}
return cf;
Probably you did not recompile your code or did not perform the FindBugs analysis again.

From my experience this can be caused by situations like this:
Situation 1 - Findbugs will complain if you only set b under some conditions, such as if a is not null, then later reference b. If a could really be null, you need to handle what to do if b is null too as a result. If a is never null, remove the null check. Also, for me it identified the line where b was defined as the first problematic line, rather than when b.doSomething() is called.
if (a != null) {
b = a.getB();
}
b.doSomething();
Situation 2 - You nullcheck in one place, but not another. Nullcheck everywhere, or nowhere
if (x != null) {
x.doSomething1();
}
x.doSomething2();

Check if Object has data or not?

I am calling method to get data as per passed text that will ping into database.
So I want to check if there is data arrived in object or not.
Code :
Method m = service.getMethodDataByFilter(text);
I have tried :
if(m == null){
System.out.println("In NULL");
}
but it does not entering inside it.
I have also tried :
if(m.getName().isEmpty()){
System.out.println("In NULL");
}
then it throws NPE in condition because no data received.
So how to check if there is data inside object or not ?
Method Class :
public class Method {
private Integer id;
private String name;
// getter-setter
}
UPDATE
Have just try Ruchira
if(m== null){
System.out.println("m is null");
}else if(m.getName()==null){
System.out.println("m.getName() is null");
}else if(m.getName().isEmpty()){
System.out.println("m.getName() is empty");
}
Still throws same NPE.
FULL Method Code :
public MethodDTO getMethod(String text){
Method m = service.getMethod(text);
if(m == null){
System.out.println("m is null");
}else if(m.getName()==null){
System.out.println("m.getName() is null");
}else if(m.getName().isEmpty()){
System.out.println("m.getName() is empty");
}
ModelMapper mapper = ModelMap.methodMapper();
return mapper.map(m, MethodDTO.class);
}

Try this if ( m == null || m.getName()== null). Note that apart from m its name may also be null.

You need to change your code to :
if(myObject==null){ // check if object is null
System.out.println("myObject is NULL");
}
else{ // myObject should not be null here
if(myObject.getField1()==null) // check for fields within the object
{
System.out.println("field1 is NULL");
}
if(myObject.getField2()==null)
{
System.out.println("field2 is NULL");
}
...
}
Note if the object is null, then trying to access any non-static field / method on it will result in NPE.

Explanation.
if(m == null){
System.out.println("In NULL");
}
Since inside if not enter since m is not null. But
if(m.getName().isEmpty()){
System.out.println("In NULL");
}
Here you get NullPointerException since m.getName() is null.
So you can try as follows
if(m == null){
System.out.println("m is null");
}else if(m.getName()==null){
System.out.println("m.getName() is null");
}else if(m.getName().isEmpty()){
System.out.println("m.getName() is empty");
}

m == null
will return false when object m is not null but it does not check all its attributes recursively inside object.
m.getName()
seems to be returning null but even this statement will not throw NPE. But yes if you call m.getName().isEmpty() will throw NPE. You should better check like this:
if (m.getName() == null) //assuming you have already checked for m being null

Check the object is null or not like this:
if(m != null && m.getName != null) {
// Object m is not null and m.getName is also not null
} else {
// Either Object m is null or m.getName is null or both are null
}