ex6_13.java

判断三角形

 //6.13（显示素数）
public class Ex6_13{
   public static void main (String[] args) {
      StackOfIntegers st=new StackOfIntegers();
      for(int i=2;i<=120;i++)
         if(isPrime(i))
         	st.push(i);
      while(!st.empty())
      	 System.out.print(st.pop() + " ");//倒序输出,即利用栈存储
      System.out.println();
   }
   public static boolean isPrime(int num){//判断素数的函数，跟前面相同
      for(int i=2;i<=num/2;i++)
      	  if(num==2) return true;
          else if(num%i==0)
          	     return false;
      return true;
   }
}

class StackOfIntegers{//书6.16节的StackOfInteger类
	private int[] elements;
	private int size;
	public StackOfIntegers(){
	   this(16);
	}
	public StackOfIntegers(int capacity){
	   elements=new int [capacity];
	}
	public int push(int value){
	   if(size>=elements.length){
	      int [] temp=new int[elements.length*2];
	      System.arraycopy(elements,0,temp,0,elements.length);
	      elements=temp;
	   }
	   return elements[size++]=value;
	}
	public int pop(){
	   return elements[--size];
	}
	public int peek(){
	   return elements[size-1];
	}
	public boolean empty(){
	   return size==0;
	}
	public int getSize(){
	   return size;
	}
}