How to use Vector in Java

Let's begin

Vector is one of the dynamic arrays in Java to store and organise the data within collections. Vector is derived from Collections and it provides flexible way to classic arrays in Java. Vector is one of the core collection for thread safe implementations.

• Dynamically Resizable: Vectors can update the size dynamically when element added or removed.
• Ordered Array: Vectors store the elements in inserted order, so we can access to elements by index.
• Synchronised: Vectors are synchronised by default, and being synchronised is providing thread-safe with multi-thread operations.

We need to consider thread-safe operations are reducing the performance. Because of locking/unlocking mechanism. So please consider this difference when thread-safe is not required.

Below you can see an example of initialising of Vector class. We can initialise a vector with initial capacity or we can create directly.

import java.util.*;

class VectorExample {
    public static void main(String[] args) {
        //Initialize a Vector
        Vector<string> vec = new Vector&lt;&gt;();
        //Initialize vector with initial capacity
        Vector<string> vector = new Vector&lt;&gt;(10); 
    }
}
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We can use add, remove and get methods for organising the data within Vector.

import java.util.*;

class VectorExample {
    public static void main(String[] args) {
        //Initialize a Vector
        Vector<string> vec = new Vector&lt;&gt;(5);
        
        //Insert new data with add method
        vec.add("red");
        vec.add("green");
        vec.add("blue");
        
        // We can get elemen at specific index by get method.
        String str = vec.get(0);
        System.out.println(str); //red
        
        // We can remove element with specific index
        vec.remove(0);
        // We can remove element by the value. This will remove first occurance
        vec.removeElement("green");
        
        // We can get the number of element with size
        int size = vec.size(); //1
        // We can get the capacity with capacity method
        int capacity = vec.capacity(); //5
        
        System.out.println(size);
        System.out.println(capacity);
    }
}
</string>

red
1
5

We can iterate the a vector with traditional for loop, with help of iterator and java streams. Below you can see the examples of iterating a Vector.

import java.util.*;

class VectorExample {
    public static void main(String[] args) {
        //Initialize a Vector
        Vector<string> vec = new Vector&lt;&gt;();

        vec.add("the");
        vec.add("code");
        vec.add("program");
        
        for(String val: vec){
            System.out.println(val);
        }
        
        Iterator<string> it = vec.iterator();
        while (it.hasNext()) {
            String val = it.next();
            System.out.println(val);
        }
        
        vec.stream().forEach(val -&gt; {
            System.out.println(val);
        });
    }
}
</string></string>

Conclusion

Vectors are providing the to store and organise data, one of main benefit of Vectors is they are suitable at thread safe operations as they are synchronised. But for sure thread-safety comes with some performance loss. If you do not need thread-safety you may also consider to use ArrayList for better performance.

That is all.

Burak Hamdi TUFAN