suanshu.java

前缀式转后缀式 simplestack是一个接口 stack是栈 suanshu是一个转换的类

public class Suanshu{
	String houstr;
	char frontstr;
	Stack mystack;
	int b;
	public int compare(char op){
		switch(op){
			case'(':
			case'#':return 1;
			case'+':
			case'-':return 2;
			case'*':
			case'/':return 3;			
		}
		return -1;
	}
	public Suanshu()throws Exception{
	mystack=new Stack();
	mystack.push('#');
	houstr=new String();	
	System.out.println ("input frontstr");
	while((frontstr=(char)(b=System.in.read ()))!='#'){
		switch(frontstr){
			case '0':
			case '1':	
			case '2':
			case '3':
			case '4':
			case '5':
			case '6':
			case '7':
			case '8':
			case '9': houstr=houstr+frontstr;break;
			case '(':mystack.push(frontstr);
				System.out.println ("now  push "+ mystack.getTop());
				break;
			case ')':
			case '#':while(mystack.getTop()!='(' && mystack.getTop()!='#'){
				houstr=houstr+mystack.pop();
				System.out.println ("123");
			}break;
			case'+':
			case'-':
			case'*':
			case'/':while(compare(frontstr)<=compare(mystack.getTop())){
				//	System.out.println ("345");
					houstr=houstr+mystack.pop();
				}mystack.push(frontstr);
				System.out.println ("now push " + mystack.getTop());
				break;													
		    }
		}
		while(mystack.getTop()!='#'){
			if(mystack.getTop()=='('){
				mystack.pop();
			}
			houstr=houstr+mystack.pop();
		}
		houstr=houstr+'#';
		System.out.println (houstr);
	}
	public static void main(String[] args)throws Exception{
	
	      new Suanshu();
	}
}