CODEWITHSUNDEEP
java
Sangeet
Sangeet

Reputation: 145

Checking for instanceOf but not executing

  private void createObject(List<Activities> listOfActivities){
    ABC object1 = new ABC();
    String value = "";
    if (listOfActivities instanceof XYZ) {
        for (Activities list: listOfActivities) {
            value= ((XYZ) list).getValue();
        }
        object1.setValue(value)
        listOfActivities.add(object1);
      }
  }

In this method, listOfActivities has some values of Type XYZ. So 'if' block should execute which is checking if listOfActivities is an instance of class XYZ, but its not executing. Why?

Thanks in advance.

Upvotes: 0

Views: 40

Answers (1)

Basil Bourque
Basil Bourque

Reputation: 338496

A List<String> is of type List, not String.

So your List<Activity> is of type List and will return false for instanceof Activity.

The objects you retrieve from the list will be of type Activity.

For this scenario:

List< Activity > list = new ArrayList<>() ;
list.add( new Activity() ) ;

…let’s try:

boolean isListAnActivity = list instanceof Activity ;  // false
boolean isElementOfListAnActivity = list.get( 0 ) instanceof Activity ;  // true

See this code run live at IdeOne.com.

isListAnActivity: false

isElementOfListAnActivity: true

Upvotes: 1

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