Thread Safe Collections in Java

Thread-Safe Collections in Java

Thread-Safe Collections in Java

A thread-safe class ensures that its internal state and method returns are accurate even when they are called simultaneously from different threads. Java’s thread-safe collection classes include Stack, Vector, Properties, Hashtable, etc.

Using thread safe collections in Java can be an effective way to avoid memory leaks and memory consumption. However, there are some caveats.


Stack safe collections in Java are a collection type that is thread-safe and fail-fast by design. They are also thread-safe because they are client-side locked. This means that another thread cannot access any of the methods in a collection. This is important because it helps prevent the other threads from accessing the data. This can affect throughput.

The Java Collection Framework provides several classes which represent a group of elements. These include the Stack and Vector, classes. There are also several interfaces which represent groupings of elements. Each interface is designed to allow an implementation to perform a specific function. Stack and Vector can be used for a variety of applications, including processing function calls and backtracking.

The Stack class is a subclass of Vector. It implements the last-in, first-out (LIFO) data structure. In a LIFO operation, an element is removed or added from the top of the stack. There is also a method for checking whether the stack is empty, called peek. It looks at the object on the top of the stack and returns the top element. If the object is not on the top of the stack, it will return a false value.

The Stack class also implements several other methods. They include the push-and-pop methods. The push method adds an object to the top of the stack. It also implements a synchronized version of push, which is thread-safe in a multithreaded environment.


ArrayList and Vector are two types of thread-safe collections in Java. They are similar in that they use an Array for holding their contents, but they are not necessarily the same. They can have different sizes and are synchronized or not. They both allow duplicates but differ in how they manage their insertion order.

ArrayList uses an array data structure and allows for null values. It also can grow or shrink to accommodate new items. It has a default initial size of 10 and can grow to half of that size if needed.

Vector is a class that combines the synchronization and resizable array of ArrayList with the performance of an Iterator. It has several legacy methods, but most programmers are still inclined to use an Iterator. It also can return Enumeration objects, which are faster than an Iterator.

The Vector class has several methods: clone, equals, equals, and last element. It has a setSize method, which explicitly sets the size of the Vector. It also has a settlement method, which sets the component at a given index as an object. It also has a function, ensure capacity, which increases the capacity of the Vector. It also has a function, remove, which removes the first element in the Vector.


It also has a search function, which traverses the elements of the Vector starting at the given index. It returns the index of the first element found. If it cannot find the element, it returns -1.


Using thread-safe collections in Java can be an efficient approach to creating a multithreaded application. But it can also lead to unexpected results. Fortunately, there are a few methods to help you avoid these pitfalls.

A thread-safe collection is one that guarantees that the internal state of a class will behave correctly when invoked concurrently by multiple threads. There are two basic ways to do this: synchronization and immutable data types.

Synchronization is one of the main ways to prevent races, and there are several implementations of this type in Java. In addition, a thread-safe data type can safely store and share mutable data.

Immutable data types, on the other hand, are types of data that will not change when shared between threads. This allows them to be shared safely between threads, and their internal state is never corrupted.

The Java Collections framework implements several well-known data structures. It also provides several wrapper methods to make these collections thread-safe.

The Properties class is one of the thread-safe collection classes. The Properties class is a reusable object representing a persistent property set. This class allows multiple threads to share a single Properties object without the need for synchronization. It also has a put method that allows the caller to insert entries whose keys are not Strings.

The Stack class is another example of a thread-safe collection. The Stack class is based on the LIFO (last-in, first-out) principle. The Stack class provides several methods to support various operations, including push, read, and peek. The Stack class also provides a synchronized operation, which means that all operations are done in an atomic fashion.


Objects used as keys in a Hashtable must implement the equals method. In addition, the key must be unique. If a key has been used before, it must be recreated.


There are better options for storing data in a specified order than a Hashtable. The best option is to use an external synchronized object. A Hashtable is not very efficient, but it is thread-safe. Therefore, it is a good choice if you are working with unordered data.

Hashtables are an excellent choice if you are working on a multithreaded application. The keys are used to retrieve items from the Hashtable. If you are storing data in a specific order, you will be better off using a more efficient data structure.

Hashtable is a subclass of Dictionary. It is a legacy class in the JDK. It is part of the Collections framework. It stores key-value pairs and uses synchronized methods to ensure thread safety.

Unlike Hashtable, HashMap does not provide thread safety. The enumeration of HashMap uses an iterator. The iterator is not fail-safe, however. The HashMap iterator throws a ConcurrentModificationException if you modify it concurrently.

The contains() method checks if an entry is in the Hashtable. Depending on the implementation, the contains method may return true or false. If there are no entries in the Hashtable, the contains method will return a boolean, indicating that the Hashtable is empty.

If the keys and values in the Hashtable are mapped, the hashtable method is responsible for replacing the values with new ones. The replace method returns an actual value if the keys are identical. If the keys are different, the replace method returns false.


Using Java Collections is easy and safe but not thread-safe by default. Object-level synchronization is necessary to prevent the possibility of an inconsistent result. This article will explore several methods to create thread-safe collections in Java.

The Collections framework provides a variety of utility classes and implementations of common data structures. Most collections are optimized for single-threaded applications. However, using “concurrent” classes may be more appropriate when a collection is shared between multiple threads.

“Concurrent” collections use a Lock or ConcurrentHashMap to handle concurrent access. This enables multiple threads to access different segments of the map at the same time. The Lock uses a different mutex for each segment. The ConcurrentHashMap package includes several implementations of this type of map.

The synchronized seat method accepts a Set interface object. It then returns a synchronized set of objects backed by the specified collection. This method works best when the collection is extensive.

The Set interface also provides methods to iterate over an object. The Collection interface provides methods to add elements to the collection, remove elements, and count elements. Generally, a collection is fail-fast, meaning it will not update an element if it is being modified. However, this does not mean it is safe to modify an immutable array or object while it is being iterated. If the elements in the iterator change during an iteration, the iterator will throw a ConcurrentModificationException.


Using synchronized list thread-safe collections in Java is an excellent way to ensure that the internal state of a class is correct when it is invoked concurrently from multiple threads. The Java platform provides various synchronization wrappers to help avoid errors and deadlocks.

The first step is determining which type of synchronized collections are most appropriate for your application. The Java Collections framework offers an extensive set of interfaces to help you handle different types of collections.

Several types of synchronized collections include synchronized List, synchronized Set, and synchronized SortedMap. The first is the most basic and provides a thread-safe implementation of List and Map conditionally.

The second is a thread-safe variant of ArrayList. This method creates a new synchronized ArrayList backed by a specified list. In addition, this method uses a lock to prevent concurrent modification errors.

The synchronized List may also be obtained by calling Collections. Synchronized List (). It is a simple method and is one of the easiest ways to synchronize a Java class.

Another option for synchronizing collections in Java is CopyOnWriteArrayList. It is more scalable than Vector and is a good choice for arrays that are read or written. The CopyOnWriteArrayList method creates a synchronized list by executing a copy of the underlying array. The List is then replaced by the copy. The new List can be used to perform thread-safe mutating operations.

How can a collection be made thread-safe in Java?

The synchronized list() function may be used to create an ArrayList that is thread-safe. Let’s examine the inner workings of this approach. A static inner class named SynchronizedList is contained in the Collections class. When this class’s object is returned, the synchronized list() function is invoked.


Why are collections in Java not thread-safe?

The majority of the objects in the Collections classes (including ArrayList, LinkedList, HashMap, etc.) are non-synchronized, meaning that many threads may work on an object at the same time since they are not thread-safe objects.

Which collections all have thread safety?

A class that is thread-safe ensures that its internal state and method returns are accurate even when they are called simultaneously from different threads. For example, Java’s thread-safe collection classes include Stack, Vector, Properties, Hashtable, etc.

Which class is thread-unsafe?

Make sure the class is “thread-safe” when creating a class that can be used for concurrent programming or a class whose instances may be utilized by several threads simultaneously. In Examples 2-7, the IntList class is a good example. No threads are safe in this class.

What is referred to as thread-safe?

Even when multiple threads enter the same piece of thread-safe code concurrently, it functions as intended. This frequently implies that internal data structures or actions that must continue without interruption are shielded from several alterations at once.