Java Study Notes 27, java Study Notes

Java Study Notes 27, java Study Notes

Vector is the implementation class of the List interface and supports all functions of the List interface. The Vector class is a List class implemented based on arrays and encapsulates a dynamic,

The Object [] array that allows redistribution. The Vector is thread-safe and requires no program to ensure the synchronization of the set.

Some methods of the Vector class are described as follows:

Public class Main {public static void main (String [] args) {Vector vector = new Vector (); ArrayList list = new ArrayList (); list. add ("BILL"); vector. add (list); // output: [[BILL] System. out. println (vector); // output: vector capacity: 10System. out. println ("vector capacity:" + vector. capacity ();/** increase the capacity of this vector (if necessary) to ensure that it can save at least the number of components specified by the minimum capacity parameter. * If the current capacity of this vector is smaller than minCapacity, replace its internal data array (saved in the field elementData) * with a large array to increase its capacity. The size of the new data array will add capacityIncrement to the original size. * unless the value of capacityIncrement is smaller than or equal to zero, in the latter case, the new capacity will be twice the original capacity, * However, if the size is still smaller than minCapacity, The new capacity will be minCapacity. */Vector. ensureCapacity (21); // output: vector capacity: 21System. out. println ("vector capacity:" + vector. capacity (); Vector vector1 = new Vector (); vector1.add (list);/** returns true */System if the specified Object is equal to this Vector. out. println (vector. equals (vector1); // output: true/** returns the item at the first component of the vector (index 0 ). */System. out. println (vector. firstElement (); // output: [BILL]/** returns the element at the specified position in the vector. * If the index is out of the range (index <0 | index> = size (), an ArrayIndexOutOfBoundsException exception is thrown */System. out. println (vector. get (0); // output: [BILL]/** returns the hash value of this vector. */System. out. println (vector. hashCode (); vector. add ("JACK"); vector. add ("MARRAY"); vector. add ("JACK"); // output: [[BILL], JACK, MARRAY, JACK] System. out. println (vector);/** returns the index of the specified element that appears for the first time in this vector. If this vector does not contain this element,-1 is returned. More specifically, * returns true (o = null? Get (I) = null: the lowest index I of o. equals (get (I); * if no such index exists,-1 is returned. */System. out. println (vector. indexOf ("JACK"); // output: 1/** returns the index of the specified element that appears for the first time in this vector. The index is positively searched, * If this element is not found,-1 is returned. * If the specified index is negative, an IndexOutOfBoundsException exception is thrown */System. out. println (vector. indexOf ("JACK", 2); // output: 3/** Insert the specified object as a component in this vector to the specified index. * Each component in this vector whose index is greater than or equal to the specified index will shift up. * change the index value to a value greater than 1 in the past. The index must be a value greater than or equal to 0 and * less than or equal to the current vector size (if the index is equal to the current vector size, * the new element is added to the vector ). * If the index is out of the range (index <0 | index> size (), an ArrayIndexOutOfBoundsException exception is thrown */vector. insertElementAt ("WORD", 1); // output: [[BILL], WORD, JACK, MARRAY, JACK] System. out. println (vector);/** returns true if and only if this vector has no components (that is, its size is zero); otherwise, false. */System. out. println (vector. isEmpty (); // output: false/** returns the index of the last occurrence of the specified element in this vector. If this vector does not contain this element,-1 is returned. More specifically, * returns true (o = null? Get (I) = null: the highest index I * of o. equals (get (I); if no such index exists,-1 is returned. */System. out. println (vector. lastIndexOf ("JACK"); // output: 4/** remove the element at the specified position in the vector. Remove all subsequent elements to the left (delete the index by 1 ). Returns the removed element from the vector. * If the index is out of the range (index <0 | index> = size (), an ArrayIndexOutOfBoundsException exception is thrown */vector. remove (0); // output: [WORD, JACK, MARRAY, JACK] System. out. println (vector);/** removes the first matching item of the specified element in this vector. If the vector does not contain this element, the element remains unchanged. * To be more precise, the removal of its index I satisfies (o = null? Get (I) = null: o. equals (get (I) * element (if such an element exists ). */System. out. println (vector. remove ("WORD"); System. out. println (vector); // output: [JACK, MARRAY, JACK]}

For more information about the Vector method, see subsequent articles.

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