Java implements a stack

Package zhangtingting; public class stacktest {private object [] stack; // number of elements; private int size; // The default length is 10; Public stacktest () {This (10 );} // You can also set the length, that is, capacity. Public stacktest (INT Len) {stack = new object [Len];} // returns the number of elements. Public int size () {return size;} // return the length of the array, that is, capacity. Public int capacity () {return stack. length ;}// implement a dynamic array; Public void ensurecapacity () {If (SIZE () = capacity () {object [] newstack = new object [size () * 3 /2 + 1]; system. arraycopy (stack, 0, newstack, 0, size (); stack = newstack ;}/// inbound stack; Public void push (Object O) {size ++; ensurecapacity (); stack [size-1] = O;} // empty; Public Boolean isempty () {return size = 0;} // out stack; public object POP () {// you must first specify NULL; If (isempty () {Throw new arrayindexoutofboundsexception ("cannot be blank ");} object o = stack [-- size]; stack [size] = NULL; return O;} public static void main (string [] ARGs) {stacktes T stack = new stacktest (3); string [] DATA = new string [] {"A", "B", "C"}; For (INT I = 0; I <data. length; I ++) {stack. push (data [I]); system. out. println (data [I] + "");} system. out. println ("************"); While (! Stack. isempty () {system. Out. println (stack. Pop () + "");}}}