opplus.java

用JAVA写的计算一段数学表达式的程序

package net.csksoft.util.expcomp;
import java.util.*;
public class OpPlus extends OperationToken {

//Finish CodeFans.net
	public boolean Calc(Stack<OpObj> objStack) {
		switch (this.getArgNum())
		{
		case 1:
			return this.Calc1(objStack);
		case 2:
			return this.Calc2(objStack);
		default:
			return false;
		}
	}
	private boolean Calc2(Stack<OpObj> objStack)
	{
		OpObj a,b,ans;
		if (objStack.isEmpty()) return false;
		b = objStack.pop();
		if (objStack.isEmpty()) return false;
		a = objStack.pop();
		try
		{
			ans = (OpObj)new NumberToken(a.getValue() + b.getValue());
		}
		catch(Exception exp)
		{
			return false;
		}
		objStack.push(ans);
		return true;
	}
	private boolean Calc1(Stack<OpObj> objStack)
	{
		OpObj a,ans;
		
		if (objStack.isEmpty()) return false;
		a = objStack.pop();
		try
		{
			ans = (OpObj)new NumberToken(- a.getValue());
		}
		catch(Exception exp)
		{
			return false;
		}
		objStack.push(ans);
		return true;
	}	
	public boolean setArgNum(int newArg)
	{
		if (newArg==1 || newArg == 2)
		{
			arg_num = newArg;
			return true;
		}
		else
		{
			return false;
		}
	}

}