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javaobjectscope
geofrey rainey
geofrey rainey

Reputation: 342

Java Object Scope

I am trying to create an object based on a condition, therefore the object creation is within the conditional's scope, however I need to see the object outside of that scope. I thought adding it to a Map would work, but it doesn't. Consider the following example:

TestModel.java

public class TestModel {
private String text;
public void setText(String text){
this.text = text;}
public String getText(){
return this.text;}
}

ScopeTest.java

import java.util.*;
class ScopeTest {

public static void main(String[] args) {

TestModel testModel;
Map<String, Object> myModel = new HashMap<String, Object>();

for (int i=1; i<2; i++){ // if a certain condition is met, create an object as below
    testModel = new TestModel();
    testModel.setText("test text");
    myModel.put("test", testModel);
    }

for (Map.Entry<String, Object> entry : myModel.entrySet()) {
    String key = entry.getKey();
    Object value = entry.getValue();
    System.out.println("key=" + key); // I can see the key value
    System.out.println("value.getText()=" + value.getText()); // but can't see testModel object. I am not sure how to resolve.
}
}
}

cheers,

Geofrey Rainey.

Upvotes: 0

Views: 235

Answers (4)

Pshemo
Pshemo

Reputation: 124265

Why not just use TestModel as generic type of value in your Map like below?

Map<String, TestModel> myModel = new HashMap<>();
//          ^^^^^^^^^ - instead of Object

This way you can iterate over your map with

for (Map.Entry<String, TestModel> entry : myModel.entrySet()) {
    ...
}

and you will be able to store value in 

TestModel value = entry.getValue();

without needing to cast it. Now since type of value reference will be TestModel compiler will let you use its methods like getText() without problems. 

System.out.println("value.getText()=" + value.getText());

Also I am not sure why you are using loop if you want to iterate over it once. Simple if would be better. Another thing is using Map to hold one element seems unnecessary. You can just use one reference like 

boolean someCondition = true;

TestModel testModel = null;
if (someCondition) { // if a certain condition is met, create
    testModel = new TestModel();
    testModel.setText("test text");
}

if (testModel!=null){
    System.out.println(testModel.getText());
}

Upvotes: 0

Vinayak Pingale
Vinayak Pingale

Reputation: 1315

You have to cast the Object value with your Class. Like this.

System.out.println("value.getText()=" + ((TestModel) value).getText());

If you dont want to cast the object then you can use like this.

class ScopeTest {

public static void main(String[] args) {

TestModel testModel;
Map<String, TestModel> myModel = new HashMap<String, TestModel>();//Use TestModel
                                                                instead of object

for (int i=1; i<2; i++){ 
    testModel = new TestModel();
    testModel.setText("test text");
    myModel.put("test", testModel);
    }

for (Entry<String, TestModel> entry : myModel.entrySet()) {
    String key = entry.getKey();
    TestModel value = entry.getValue();
    System.out.println("key=" + key); 
    System.out.println("value.getText()=" + value.getText()); 
}
}
}

Upvotes: 2

Alexander_Winter
Alexander_Winter

Reputation: 314

You should cast the Object into your model.

TestModel value = (TestModel) entry.getValue();

Upvotes: 1

fedorSmirnov
fedorSmirnov

Reputation: 711

I think you might have to cast the object returned by the HashMap to be a TestModel before you can use a method of that class.

Upvotes: 0

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