java 8 nested null check list of objects - java-8

Question

I am trying to do a nested null check and then clear the values in map in the nested object if the map is not null.
The following is my hypothetical code. I am wondering if this is the right way to do it or is there a more elegant solution to this.
package exp.myJavaLab.Experiments;
import java.util.*;
public class OptionalTest {
public Inner inner;
public static void main(String[] args) {
OptionalTest testObj = new OptionalTest();
Pojo pojo1 = new Pojo();
pojo1.id = 1;
Map<String, String> dataMap = new HashMap<>();
dataMap.put("a","b");
pojo1.dataMap = dataMap;
Pojo pojo2 = new Pojo();
pojo2.id = 2;
Inner inner = new Inner();
inner.pojoList = Arrays.asList(pojo1, pojo2);
testObj.inner = inner;
System.out.println(testObj);
Optional.ofNullable(testObj.inner)
.map(Inner::getPojoList)
.ifPresent(pojos -> pojos.forEach(pojo -> {
if (pojo.getDataMap() != null) {
pojo.getDataMap().clear();
}
}));
System.out.println(testObj);
}
#Override
public String toString() {
final StringBuilder sb = new StringBuilder("OptionalTest{");
sb.append("inner=").append(inner);
sb.append('}');
return sb.toString();
}
}
class Inner {
public List<Pojo> pojoList;
public List<Pojo> getPojoList() {
return pojoList;
}
#Override
public String toString() {
final StringBuilder sb = new StringBuilder("Inner{");
sb.append("pojoList=").append(pojoList);
sb.append('}');
return sb.toString();
}
}
class Pojo {
public Map<String, String> dataMap;
public int id;
#Override
public String toString() {
final StringBuilder sb = new StringBuilder("Pojo{");
sb.append("dataMap=").append(dataMap);
sb.append(", id=").append(id);
sb.append('}');
return sb.toString();
}
public Map<String, String> getDataMap() {
return dataMap;
}
public int getId() {
return id;
}
}

Answer 1

In my opinion Collections should never be null.
You could declare your pojoList and dataMap as private and instantiate them.
Your class then needs some add-methods. So you are sure getDataMap() never returns null:
class Pojo {
private Map<String, String> dataMap = new HashMap<>();
public Map<String, String> getDataMap() {
return dataMap;
}
public void add(String key, String value) {
dataMap.put(key, value);
}
}
Then you don't need to check for null:
Optional.ofNullable(testObj.inner)
.map(Inner::getPojoList)
.ifPresent(pojos -> pojos.forEach(pojo -> { pojo.getDataMap().clear(); }));