I am new for Java . I was just looking for the Iterator in Collection Framework. but now I want to remove all null from ArrayList by using Iterator's remove() method .so tried following code but I am not getting expected output as I want a list without any null values . please explain someone Thank you.
here is my code
package setinterface;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
public class InternalWorkingOfArrayList {
public static void main(String[] args) {
List<String> setOfString = new ArrayList<String>();
setOfString.add("A");
setOfString.add("B");
setOfString.add("C");
setOfString.add("B");
setOfString.add(null);
setOfString.add("A");
setOfString.add(null);
Iterator<String> iterator = setOfString.iterator();
while (iterator.hasNext()) {
String string = (String) iterator.next();
if (null==string) {
iterator.remove();
break;
}
}
for (String string1 : setOfString) {
System.out.println(string1);
}
}
}
Why are you breaking the loop?? Remove break statement from your code.
while (iterator.hasNext()) {
String string = (String) iterator.next();
if (null==string) {
iterator.remove();
//break;
}
}
What you are doing wrong here is that you are directly trying to cast your element into string. This would give you an exception for a null element.
This is what you could do precisely.
package setinterface;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
public class InternalWorkingOfArrayList {
public static void main(String[] args) {
List<String> setOfString = new ArrayList<String>();
setOfString.add("A");
setOfString.add("B");
setOfString.add("C");
setOfString.add("B");
setOfString.add(null);
setOfString.add("A");
setOfString.add(null);
Iterator<String> iterator = setOfString.iterator();
while (iterator.hasNext()) {
if (null==iterator.next()) {
iterator.remove();
}
}
for (String string1 : setOfString) {
System.out.println(string1);
}
}
}
Using Java-8 features, you can achieve it with a single line of code in following way...
setOfString.removeAll(Collections.singleton(null));
And then print the output:
System.out.println(setOfString); //output would be: [A, B, C, B, A]
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