How to make an ArrayList read only in Java
Given an ArrayList, the task is to make this ArrayList read-only in Java.
Input: ArrayList: [1, 2, 3, 4, 5] Output: Read-only ArrayList: [1, 2, 3, 4, 5] Input: ArrayList: [geeks, for, geeks] Output: Read-only ArrayList: [geeks, for, geeks]
An ArrayList can be made read-only easily with the help of Collections.unmodifiableList() method. This method takes the modifiable ArrayList as a parameter and returns the read-only unmodifiable view of this ArrayList.
readOnlyArrayList = Collections.unmodifiableList(ArrayList);
Below is the implementation of the above approach:
Initial list: [X, Y, Z] ReadOnly ArrayList: [X, Y, Z] Trying to modify the ReadOnly ArrayList. Exception thrown : java.lang.UnsupportedOperationException
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