由于电脑突然出了点问题,我没有完成mini DC这个测试,现将测试内容及结果补交
题目如下
提交测试截图和码云练习项目链接,实现Linux下dc的功能,计算后缀表达式的值
import com.sun.xml.internal.fastinfoset.util.CharArray;
import java.util.StringTokenizer;
import java.util.Stack;
public class MyDC {
/**
* constant for addition symbol
*/
private final char ADD = '+';
/**
* constant for subtraction symbol
*/
private final char SUBTRACT = '-';
/**
* constant for multiplication symbol
*/
private final char MULTIPLY = '*';
/**
* constant for division symbol
*/
private final char DIVIDE = '/';
/**
* the stack
*/
private Stack<Integer> stack;
public MyDC() {
stack = new Stack<Integer>();
}
public int evaluate(String expr) {
int op1, op2, result = 0;
String token;
StringTokenizer tokenizer = new StringTokenizer(expr);
while (tokenizer.hasMoreTokens()) {
token = tokenizer.nextToken();
//如果是运算符,调用isOperator
if (isOperator(token)==true) {
op2=stack.pop();
op1=stack.pop();
//从栈中弹出操作数2
//从栈中弹出操作数1
result=evalSingleOp(token.charAt(0),op1,op2);
//根据运算符和两个操作数调用evalSingleOp计算result;
stack.push(result);
//计算result入栈;
}
else//如果是操作数
{
stack.push(Integer.parseInt(token));
}
//操作数入栈;
}
return result;
}
private boolean isOperator(String token) {
return (token.equals("+") || token.equals("-") ||
token.equals("*") || token.equals("/"));
}
private int evalSingleOp(char operation, int op1, int op2) {
int result = 0;
switch (operation) {
case ADD:
result = op1 + op2;
break;
case SUBTRACT:
result = op1 - op2;
break;
case MULTIPLY:
result = op1 * op2;
break;
case DIVIDE:
result = op1 / op2;
}
return result;
}
}
* **MyDCTester.class**
import java.util.Scanner;
public class MyDCTester {
public static void main (String[] args) {
String expression, again;
int result;
try
{
Scanner in = new Scanner(System.in);
do
{
MyDC evaluator = new MyDC();
System.out.println ("Enter a valid postfix expression: ");
expression = in.nextLine();
result = evaluator.evaluate (expression);
System.out.println ("That expression equals " + result);
System.out.print ("Evaluate another expression [Y/N]? ");
again = in.nextLine();
System.out.println();
}
while (again.equalsIgnoreCase("y"));
}![](http://images2015.cnblogs.com/blog/1071653/201705/1071653-20170503220452023-968944949.jpg)
catch (Exception IOException)
{
System.out.println("Input exception reported");
}
}
}