Simple use of Vector in Java

Similar to vector in C ++, it can also store various types of elements.

Import java. util. vector;

Eg.

Vector ivec = new vector ();

Vector ivec = new vector (10); // ivec with an initial length of 10

Vector ivec = new vector (10, 5); // The initial length is 10. When the space is insufficient, the length increases by 5.

Ivec. Add (5); // Add element 5

Ivec. Add (INT index, object value); // Add the element value at the index position. After insertion, other elements are removed.

Ivec. Set (INT index, object value); // change the element value with index to value.

Object OBJ = ivec. Get (INT index); // obtain the value of the element whose index is index.

Ivec. Remove (INT index); // Delete the element whose index is located.

Ivec. tostring (); // converts all elements into strings for output.

When deleting all elements from a vector in C ++ and C ++, you must note that deleting an element in C ++ will invalidate the iterator, as shown below:

For (STD: vector <int >:: iteator iter = VEC. Begin (); iter! = Vec. End (); ++ ITER)

{

VEC. Erase (ITER); // error! This will not delete all elements correctly.

}

The reason why all elements cannot be deleted correctly is that the iterator fails after Vec. Erase (ITER), which should be written in the following method:

For (STD: vector <int >:: iteator iter = VEC. Begin (); iter! = Vec. End ();)

{

If (condition)

{

Iter = Vec. Erase (ITER); // Save the value of each iterator. After deletion, ITER points to the next element to be deleted.

}

Else

{

++ ITER;

}

}

Similarly, when deleting all elements in Java:

For (INT I = 0; I <ivec. Size ();)

{

Ivec. Remove (I); // or ivec. Remove (0 );

}

System. Out. println ("output all elements in string form:" + ivec. tostring ());