ex8_4.java

判断三角形

//8.4
public class Ex8_4{
   public static void main (String[] args) {
      StackOfObjects st=new StackOfObjects();
      int count=0,num=2;
      while(count<50){//将50个素数按顺序放入栈中
         if(isPrime(num)){
         	st.push(new Integer(num));
         	count++;
         }
         num++;
         }
      while(!st.empty()){
      	 System.out.print(st.pop() + " ");
      	 if(st.getSize()%10==0)
      	  System.out.println();
      	 }
      System.out.println();
   }
   public static boolean isPrime(int num){//判断是否为素数，即除1和本身外能否被其他整数整除
      for(int i=2;i<=num/2;i++)
      	  if(num==2) return true;
          else if(num%i==0)
          	     return false;
      return true;
   }
}

class StackOfObjects{//StackOfObjects类，利用StackOfObjects类改写
	private Object[] elements;
	private int size;
	public StackOfObjects(){
	   this(16);
	}
	public StackOfObjects(int capacity){
	   elements=new Object[capacity];
	}
	public Object push(Object value){
	   if(size>=elements.length){
	      Object[] temp=new Object[elements.length*2];
	      System.arraycopy(elements,0,temp,0,elements.length);
	      elements=temp;
	   }
	   return elements[size++]=value;
	}
	public Object pop(){
	   return elements[--size];
	}
	public Object peek(){
	   return elements[size-1];
	}
	public boolean empty(){
	   return size==0;
	}
	public int getSize(){
	   return size;
	}
}