java - Reversing a Generic Array using "in situ" -

for generic array added method reverse() has reverse array without using additional array of elements , trying perform reverse “in situ” using swap operations. may have gotten wrong , if how can reversed “in situ” using swap operations?

import java.util.collections;  class genericarray<e> {     private e[] array;     private int size;      public genericarray() {         array = (e[]) new object[10];         size = 0;     }      public e get(int i) {         return array[i];     }      public void set(int i, e value) {         if (i < size)             array[i] = value;     }      public void add(e value) {         array[size++] = value;     }      public boolean isfull() {         return size == array.length;     }      public void remove(int i) {         (int j = i; j < size; j++)             array[j] = array[j + 1];         size--;     }      public void insert(int i, e value) {         (int j = size; j >= i; j--)             array[j + 1] = array[j];         array[i] = value;         size++;     }      public void display() {         (int = 0; < size; i++)             system.out.print(array[i] + " ");         system.out.println();     }      public e reverse() {          collections.reverse(array);      }  } 

if mean want manually without using collections.reverse (that code shouldn't compile btw, reverse needs list parameter), traverse array beginning middle swapping elements @ opposite sides of range:

public e[] reverse() {     (int = 0; < size/2; i++){         e tmp=array[i];           array[i] = array[size - - 1];         array[size - - 1]=tmp;     }     return array; // if want return } 

more info on in situ algorithms on wikipedia.

regarding add implementation ensures there enough space:

public void add(e value) {     int newsize=size+1;     if(newsize<size){         //the array big enough, add element         array[newsize]=value;     }else{         //the array small, create new 1         //the old content twice bigger , add          //the new element         array=arrays.copyof(array,size*2);          array[newsize]=value;       }     size=newsize; }