访问在Main类中创建的Map Interface对象

Question

Consider the following two classes :

Class A begins here is a separate java file in the same package:

public class A {

public void putIntoMap(int a[]){
  Map <Integer, Integer> intMapObject = new HashMap<Integer,Integer>();
      for (int i = 0 ; i < a.length ; i++){

          // some code here
       }
       intMapObject.put(a[i], count);
}


}

Class B begins here is a separate java file in the same package:

public class B {

    public static void main(String args[]){

    A a = new A();

    a.putIntoMap(arr); // assume arr is an array I already have

    // Now I need to do loop over the Map and I need the `intMapObject`  //object from above class A


// I need to do something like this 

for (Map.Entry<Integer,Integer> e : intMapObject.entrySet()){


  // some code here

     }

}

How do I access intMapObject object in class B ?

Answer 1

You can't access variables declared in another method. Ever.

But that doesn't mean you can't pass objects from one method to another. In this case, I suggest making putIntoMap return the new map:

// in A
public Map<Integer, Integer> putIntoMap(int a[]){
  Map <Integer, Integer> intMapObject = // ...
  // some code to put the stuff in the map here

  return intMapObject;
}

// in B
A a = new A();
Map<Integer, Integer> theMap = a.putIntoMap(arr);
for(Map.Entry<Integer, Integer> e : theMap.entrySet()) {
    // some code here
}

Note that this does not pass the actual object, but a reference to it. In Java, objects are not stored in variables.