public interface Mystack<T> {
    
    boolean isempty();
    
   void clear();
   
   int length();
   //入栈
   boolean push(T data);
   //出栈
   T pop();
}

package suanfa;

public class MyArrayStack<T> implements Mystack<T> {

    private Object [] obs=new Object[16];
    private int size=0;
    
    
    @Override
    public boolean isempty() {
        // TODO Auto-generated method stub
        return size==0;
    }

    @Override
    public void clear() {
        // TODO Auto-generated method stub
        for (int i=0;i<obs.length;i++){
            
            obs[i]=null;
        }
        
        size=0;
    }

    @Override
    public int length() {
        // TODO Auto-generated method stub
        return size;
    }

    @Override
    public boolean push(T data) {
        // TODO Auto-generated method stub
    //    return false;
        
        if(size>=obs.length){
            resize();
            
        }
        obs[size++]=data;
        
        return true;
        
    }

    @Override
    public T pop() {
        // TODO Auto-generated method stub

      if(size==0){
       return null;
       }
     return (T) obs[--size];

    }
    
    
    private void resize(){
        
        Object [] tmp=new Object[obs.length*3/2+1];
        
        for(int i=0;i<obs.length;i++){
            tmp[i]=obs[i];
            obs[i]=null;
            
        }
        
        obs=tmp;
        
    }

}