Question: Can We Modify List While Iterating?

Can we modify list in Python?

How to Modify Lists in Pythonappend(): Adds a new entry to the end of the list.clear(): Removes all entries from the list.copy(): Creates a copy of the current list and places it in a new list.extend(): Adds items from an existing list and into the current list.insert(): Adds a new entry to the position specified in the list.More items….

Can we remove any element by using for each loop?

Unfortunately, you cannot use it everywhere. Consider, for example, the expurgate method. The program needs access to the iterator in order to remove the current element. The for-each loop hides the iterator, so you cannot call remove .

What does iterator do in Java?

In Java, Iterator is an interface available in Collection framework in java. util package. It is a Java Cursor used to iterate a collection of objects. It is used to traverse a collection object elements one by one.

How do you check if an ArrayList is empty?

The isEmpty() method of ArrayList in java is used to check if a list is empty or not. It returns true if the list contains no elements otherwise it returns false if the list contains any element. Parameter: It does not accepts any parameter.

Can we modify collection while iterating?

It is not generally permissible for one thread to modify a Collection while another thread is iterating over it. … Actually, the right way to handle such scenario is to use Iterator to remove the element from the underlying Collection while iterating over it.

Are arrays mutable in python?

Python’s array module provides space-efficient storage of basic C-style data types like bytes, 32-bit integers, floating point numbers, and so on. Arrays created with the array. array class are mutable and behave similarly to lists—except they are “typed arrays” constrained to a single data type.

Is list iterable in python?

An object is called iterable if we can get an iterator from it. Most built-in containers in Python like: list, tuple, string etc. are iterables.

What is an important difference between lists and tuples?

We can conclude that although both lists and tuples are data structures in Python, there are remarkable differences between the two, with the main difference being that lists are mutable while tuples are immutable. A list has a variable size while a tuple has a fixed size.

How do I remove an item from an ArrayList?

There are two way to remove an element from ArrayList.By using remove() methods : ArrayList provides two overloaded remove() method. a.Using Iterator. remove() method : It is not recommended to use ArrayList. remove() when iterating over elements.

How do you use iterator in ArrayList?

Java – How to Use Iterator?Obtain an iterator to the start of the collection by calling the collection’s iterator( ) method.Set up a loop that makes a call to hasNext( ). Have the loop iterate as long as hasNext( ) returns true.Within the loop, obtain each element by calling next( ).

How do you remove an element from a list while iterating?

An element can be removed from a Collection using the Iterator method remove(). This method removes the current element in the Collection. If the remove() method is not preceded by the next() method, then the exception IllegalStateException is thrown.

Can we modify ArrayList while iterating?

Replace element in arraylist while iterating Do not use iterator if you plan to modify the arraylist during iteration. Use standard for loop, and keep track of index position to check the current element. Then use this index to set the new element. Java program to search and replace an element in an ArrayList.

Can we remove element from ArrayList while iterating?

ArrayList provides the remove() methods, like remove (int index) and remove (Object element), you cannot use them to remove items while iterating over ArrayList in Java because they will throw ConcurrentModificationException if called during iteration.

How do you remove the last element of an ArrayList?

We can pass the last elements index to the remove() method to delete the last element. remove(Object obj) : Accept object to be removed. If the ArrayList does not contain duplicates, we can simply pass the last element value to be deleted to the remove() method, and it will delete that value.

Is ArrayList thread safe?

ArrayList , on the other hand, is unsynchronized, making them, therefore, not thread safe. With that difference in mind, using synchronization will incur a performance hit. So if you don’t need a thread-safe collection, use the ArrayList .

What happens when you remove an element from an ArrayList?

An ArrayList is a consecutive list of items that can be referenced by an index. So when you delete an item, all following items will be shifted. The elements will be shifted. According to the javadoc for the remove method the remaining entries will shift back so there are no gaps.

How do you change the value of an ArrayList?

You can use the set() method of java. util. ArrayList class to replace an existing element of ArrayList in Java. The set(int index, E element) method takes two parameters, first is the index of an element you want to replace and second is the new value you want to insert.

How can I avoid ConcurrentModificationException while iterating a list?

To Avoid ConcurrentModificationException in multi-threaded environmentYou can convert the list to an array and then iterate on the array. … You can lock the list while iterating by putting it in a synchronized block. … If you are using JDK1.

Can we add elements while iterating?

3 Answers. You can’t modify a Collection while iterating over it using an Iterator , except for Iterator. remove() . This will work except when the list starts iteration empty, in which case there will be no previous element.

What iterator can throw a ConcurrentModificationException?

The iterators returned by ArrayList iterator() and listIterator() methods are fail fast: if the list is structurally modified at any time after the iterator is created, in any way except through the iterator’s own remove or add methods, the iterator will throw a ConcurrentModificationException.

How do you make an array list?

To create an array list in Java, you declare an ArrayList variable and call the ArrayList constructor to instantiate an ArrayList object and assign it to the variable: ArrayList friends = new ArrayList(); You can optionally specific a capacity in the ArrayList constructor: ArrayList friends = new ArrayList(100);