Java Vector clear()

Java Vector [Java Vector] Java Vector

clear() Vector 

public void clear()

clear() Vector Vector size() 0 capacity()

  • Vector
  • Vector (size) 0
  • Vector (capacity)
  • O(n) n Vector

Java Vector clear() removeAllElements()

public void clear() {
    removeAllElements();
}

removeAllElements() Vector null 0

public synchronized void removeAllElements() {
    modCount++;
    // null
    for (int i = 0; i < elementCount; i++)
        elementData[i] = null;
    elementCount = 0;  //
}

import java.util.Vector;

public class VectorClearExample {
    public static void main(String[] args) {
        // Vector
        Vector<String> fruits = new Vector<>();
        fruits.add("Apple");
        fruits.add("Banana");
        fruits.add("Orange");
       
        System.out.println(" Vector: " + fruits);
        System.out.println(": " + fruits.size());
       
        // clear() Vector
        fruits.clear();
       
        System.out.println(" Vector: " + fruits);
        System.out.println(": " + fruits.size());
    }
}

 Vector: [Apple, Banana, Orange]
: 3
 Vector: []
: 0

removeAllElements()

Vector<Integer> numbers = new Vector<>();
numbers.add(1);
numbers.add(2);
numbers.add(3);

// clear() removeAllElements()
numbers.clear();  // Vector
//
// numbers.removeAllElements();

clear() Vector trimToSize()

Vector<String> items = new Vector<>(20);  // 20
items.add("A");
items.add("B");
items.add("C");

items.clear();  // 20
items.trimToSize();  // (0)

Vector clear() (synchronized)

ArrayList

ArrayList clear() Vector clear() ArrayList

// Vector clear()
public synchronized void clear() {
    removeAllElements();
}

// ArrayList clear()
public void clear() {
    modCount++;
    for (int i = 0; i < size; i++)
        elementData[i] = null;
    size = 0;
}

Q1: clear()

clear() nullVector

Q2: clear() new Vector()

  • clear() Vector
  • new Vector() Vector Vector

Q3: Vector

isEmpty()

Vector<String> v = new Vector<>();
v.clear();
if (v.isEmpty()) {
    System.out.println("Vector ");
}

Vector clear() Java

Java Vector [Java Vector] Java Vector