Java List java.lang.UnsupportedOperationException
A simple List.add() and hits the following java.lang.UnsupportedOperationException
ListExample.java
package com.mkyong;
import java.util.Arrays;
import java.util.List;
public class ListExample {
public static void main(String[] args) {
List<String> str = Arrays.asList("A", "B", "C");
str.add("D");
System.out.println(str);
}
}
Output
Exception in thread "main" java.lang.UnsupportedOperationException
at java.base/java.util.AbstractList.add(AbstractList.java:153)
at java.base/java.util.AbstractList.add(AbstractList.java:111)
at com.mkyong.ListExample.main(ListExample.java:14)
Solution
The Arrays.asList returns a fixed-size list, modify is not allowed. To fix it, try this :
ListExample.java
package com.mkyong;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class ListExample {
public static void main(String[] args) {
List<String> str = new ArrayList<>(Arrays.asList("A", "B", "C"));
//List<String> str = Arrays.asList("A", "B", "C");
str.add("D");
System.out.println(str);
}
}
Output
[A, B, C, D]
References
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Consumer<List<Integer>> con=list->{
for(int i=0;i<list.size();i++) {
list.add(list.get(i)+1);
}
list.stream().forEach(System.out::println);
};
List<Integer> list=new ArrayList<>(Arrays.asList(1,2,3));
con.accept(list);
I am getting unsupported error and if I am replacing list.add() to list.set() then there is no issue .
Great Answer!