if condition is not evaluated correctly

Question

Something weird is happening with the following piece of Java test code. This was written using Spring.

ResourceType resourceType1 = new ResourceType(RESOURCE_TYPE_NAME);
resourceType1 = resourceTypeService.addResourceType(resourceType1);

ResourceType resourceType2 = new ResourceType(RESOURCE_TYPE_NAME_2);
resourceType2 = resourceTypeService.addResourceType(resourceType2);

List<ResourceType> all = resourceTypeService.getAll();
List<ResourceType> myObjects = new ArrayList<>();
for (ResourceType resourceType : all) {
    if(resourceType.getId() == resourceType1.getId()
            || resourceType.getId() == resourceType2.getId()){
        myObjects.add(resourceType);
    }
}

assertTrue(myObjects.get(0).getId() == resourceType1.getId());

When I run it, it returns IndexOutOfBounds on the .get(0) call.

This is weird because the resourceType1 and resourceType2 have the IDs inside the all list.

This is the result of debugging the code:

Resource type 1 after insert:

resourceType1 = {ResourceType@5986} 
 id = 179

Resource type 1 after insert:

resourceType2 = {ResourceType@5987} 
 id = 180

all after getAll()

all = {ArrayList@5988}  size = 37
 ..........
 35 = {ResourceType@5986} 
  id = 179
 36 = {ResourceType@5987} 
  id = 180

This was the debugging data.

Why the if condition is not fulfilled?

Update #1

Error stacktrace:

java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
    at java.util.ArrayList.rangeCheck(ArrayList.java:653)
    at java.util.ArrayList.get(ArrayList.java:429)
    at com.test.ihbs.service.ResourceTypeServiceTest.test_getAll(xxx.java:107)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:73)
    at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:82)
    at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:73)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:224)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:83)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:68)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:163)
    at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecuter.runTestClass(JUnitTestClassExecuter.java:86)
    at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecuter.execute(JUnitTestClassExecuter.java:49)
    at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassProcessor.processTestClass(JUnitTestClassProcessor.java:64)
    at org.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.processTestClass(SuiteTestClassProcessor.java:50)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at org.gradle.messaging.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:35)
    at org.gradle.messaging.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
    at org.gradle.messaging.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:32)
    at org.gradle.messaging.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:93)
    at com.sun.proxy.$Proxy2.processTestClass(Unknown Source)
    at org.gradle.api.internal.tasks.testing.worker.TestWorker.processTestClass(TestWorker.java:106)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at org.gradle.messaging.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:35)
    at org.gradle.messaging.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
    at org.gradle.messaging.remote.internal.hub.MessageHub$Handler.run(MessageHub.java:360)
    at org.gradle.internal.concurrent.DefaultExecutorFactory$StoppableExecutorImpl$1.run(DefaultExecutorFactory.java:64)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)

I might sound stupid but can you post the full error stacktrace ? — panagdu, May 24 '15 at 20:30
If id is Long you should use equals method to compare it. Maybe you have type field set to long but getId() method return Long? — jgr, May 24 '15 at 20:42
I don't think this is relevant. Java is using boxing/unboxing pretty smart so we can compare a `long` with a `Long` using `==`. I thought about using `equals` and it has the same result. — tzortzik, May 24 '15 at 20:47

score 3 · Accepted Answer · edited Jul 06 '18 at 07:12

As I said in comments you can't compare Long using == comparator. It only works for values between (-128, 127) and only if they are not created using new keyword. It works because those values are cached by JVM so comparing reference return true.

Look here or here.

1)

Integer i = 100;
Integer p = 100;
if (i == p)  System.out.println("i and p are the same.");
if(i.equals(p))  System.out.println("i and p contain the same value.");

The output is:

i and p are the same.
i and p contain the same value.

2)

Integer i = 200;
Integer p = 200;
if (i == p)  System.out.println("i and p are the same.");
if(i.equals(p))  System.out.println("i and p contain the same value.");

The output is:

i and p contain the same value.

3)

Integer i = new Integer (100);
Integer p = new Integer(100);
if(i==p) System.out.println(“i and p are the same object”);
if(i.equals(p)) System.out.println(“ i and p contain the same value”);

In this circumstance, the output is only:

i and p contain the same value

*"It only works for values between (-128, 127)"*--and created not by using `new` keyword. — Alex Salauyou, May 24 '15 at 21:03

score 0 · Answer 2 · answered Jul 28 '16 at 06:35

"==" always compare the memory location or object references of the values. equals method always compare the values.but equals also indirectly uses the "==" operator to compare the values. Integer uses Integer cache to store the values from -128 to +127.If == operator is used to check for any values between -128 to 127 then it returns true. for other than these values it returns false .

Refer the link for some additional info.

if condition is not evaluated correctly

2 Answers2