简易Java控制台计算器

简易Java控制台计算器

源码清单：

import java.io.*;     

import java.util.*;     


public class Expression...{ 


    private ArrayList expression = new ArrayList();// 存储中序表达式     

    

    private ArrayList right = new ArrayList();// 存储右序表达式     

    

    private String result;// 结果     

    

    // 依据输入信息创建对象，将数值与操作符放入ArrayList中     

    private Expression(String input) ...{     

        StringTokenizer st = new StringTokenizer(input, "+-*/()", true);     

        while (st.hasMoreElements()) ...{     

            expression.add(st.nextToken());     

        }     

    }     

    

    // 将中序表达式转换为右序表达式     

    private void toRight() ...{     

        Stacks aStack = new Stacks();     

        String operator;     

        int position = 0;     

        while (true) ...{     

            if (Calculate.isOperator((String) expression.get(position))) ...{     

                if (aStack.top == -1    

                        || ((String) expression.get(position)).equals("(")) ...{     

                    aStack.push(expression.get(position));     

                } else ...{     

                    if (((String) expression.get(position)).equals(")")) ...{     

                        if (!((String) aStack.top()).equals("(")) ...{     

                            operator = (String) aStack.pop();     

                            right.add(operator);     

                        }     

                    } else ...{     

                        if (Calculate.priority((String) expression     

                                .get(position)) <= Calculate     

                                .priority((String) aStack.top())     

                                && aStack.top != -1) ...{     

                            operator = (String) aStack.pop();     

                            if (!operator.equals("("))     

                                right.add(operator);     

                        }     

                        aStack.push(expression.get(position));     

                    }     

                }     

            } else    

                right.add(expression.get(position));     

            position++;     

            if (position >= expression.size())     

                break;     

        }     

        while (aStack.top != -1) ...{     

            operator = (String) aStack.pop();     

            right.add(operator);     

        }     

    }     

    

    // 对右序表达式进行求值     

    private void getResult() ...{     

        this.toRight();     

        Stacks aStack = new Stacks();     

        String op1, op2, is = null;     

        Iterator it = right.iterator();     

    

        while (it.hasNext()) ...{     

            is = (String) it.next();     

            if (Calculate.isOperator(is)) ...{     

                op1 = (String) aStack.pop();     

                op2 = (String) aStack.pop();     

                aStack.push(Calculate.twoResult(is, op1, op2));     

            } else    

                aStack.push(is);     

        }     

        result = (String) aStack.pop();     

        it = expression.iterator();     

        while (it.hasNext()) ...{     

            System.out.print((String) it.next());     

        }     

        System.out.println("=" + result);     

    }     

    

    public static void main(String avg[]) ...{     

        try ...{     

            System.out.println("Input a expression:");     

            BufferedReader is = new BufferedReader(new InputStreamReader(     

                    System.in));     

            for (;;) ...{     

                String input = new String();     

                input = is.readLine().trim();     

                if (input.equals("q"))     

                    break;     

                else ...{     

                    Expression boya = new Expression(input);     

                    boya.getResult();     

                }     

                System.out     

                        .println("Input another expression or input 'q' to quit:");     

            }     

            is.close();     

        } catch (IOException e) ...{     

            System.out.println("Wrong input!!!");     

        }     

    }     

}     

class Calculate ...{     

    // 判断是否为操作符号     

    public static boolean isOperator(String operator) ...{     

        if (operator.equals("+") || operator.equals("-")     

                || operator.equals("*") || operator.equals("/")     

                || operator.equals("(") || operator.equals(")"))     

            return true;     

        else    

            return false;     

    }     

    

    // 设置操作符号的优先级别     

    public static int priority(String operator) ...{     

        if (operator.equals("+") || operator.equals("-")     

                || operator.equals("("))     

            return 1;     

        else if (operator.equals("*") || operator.equals("/"))     

            return 2;     

        else    

            return 0;     

    }     

    

    // 做2值之间的计算     

    public static String twoResult(String operator, String a, String b) ...{     

        try ...{     

            String op = operator;     

            String rs = new String();     

            double x = Double.parseDouble(b);     

            double y = Double.parseDouble(a);     

            double z = 0;     

            if (op.equals("+"))     

                z = x + y;     

            else if (op.equals("-"))     

                z = x - y;     

            else if (op.equals("*"))     

                z = x * y;     

            else if (op.equals("/"))     

                z = x / y;     

            else    

                z = 0;     

            return rs + z;     

        } catch (NumberFormatException e) ...{     

            System.out.println("input has something wrong!");     

            return "Error";     

        }     

    }     

}    

//栈类      

class Stacks...{      

   private LinkedList list=new LinkedList();      

   int top=-1;      

   public void push(Object value)...{      

      top++;      

      list.addFirst(value);      

   }      

   public Object pop()...{      

      Object temp=list.getFirst();      

      top--;      

      list.removeFirst();      

      return temp;      

    

   }      

   public Object top()...{      

   return list.getFirst();      

   }      

}