栈实现综合计算器 java 详细讲解

案例

解题思路

代码实现

package com.qf.stack;public class Caculator {    public static void main(String[] args) { StackArray numArray=new StackArray(20); StackArray operateArray=new StackArray(20); int index=0; int num1=0; int num2=0; int res=0; String funNum=""; String expression="7*2*2-5+1-5+3-4"; for (int i = 0; i < expression.length(); i++) {     char ch=expression.subSequence(i,i+1).charAt(0);     if (StackArray.isOperate(ch)){  //3.1 如果发现当前的符号栈为 空，就直接入栈  //3.2 如果符号栈有操作符，就进行比较,如果当前的操作符的优先级小于或者等于栈中的操作符， 就需要从数栈中pop出两个数,在从符号栈中pop出一个符号，进行运算，将得到结果，入数栈，然后将当前的操作符入符号栈，  // 如果当前的操作符的优先级大于栈中的操作符， 就直接入符号栈.  if (operateArray.isEmpty()){      operateArray.push(ch);  }else{      int peek = operateArray.peek();      int local = operateArray.priority((char) peek);      int chars = operateArray.priority(ch);      if (local>=chars){   num1 = numArray.pop();   num2 =numArray.pop();   int pop = operateArray.pop();   int cal = StackArray.cal(num1, num2, (char) pop);   numArray.push(cal);   operateArray.push(ch);      }else{   operateArray.push(ch);      }  }     }else{  funNum+=ch;  if (i==expression.length()-1){      numArray.push(Integer.parseInt(funNum));  }else {      if (StackArray.isOperate(expression.subSequence(i + 1, i + 2).charAt(0))) {   numArray.push(Integer.parseInt(funNum));   funNum="";      }  }     } } while (true){     if (operateArray.isEmpty()){  break;     }     num1 = numArray.pop();     num2 =numArray.pop();     int pop = operateArray.pop();     int cal = StackArray.cal(num1, num2,  pop);     numArray.push(cal); } if (operateArray.isEmpty()){     res=numArray.pop();     System.out.println("结算得到的结果："+expression+":"+res); }    }}class StackArray {    public int maxSize;    public int top;    public int [] stack;    //初始化    public StackArray(int maxSize){ this.maxSize=maxSize; this.top=-1; this.stack=new int[maxSize];    }    //栈是否已满    public boolean isFull(){ return top==maxSize-1;    }    //栈是否为空    public boolean isEmpty(){ return top==-1;    }    //入栈    public void push(int num){ if (isFull()){     System.out.println("栈已满，请出栈~~~"); }else{     top++;     stack[top]=num; }    }    //获取栈顶元素    public int peek(){return stack[top];}    //出栈    public int pop(){ if (isEmpty()){     throw new RuntimeException("栈为空，请入栈~~~"); } int value=stack[top]; top--; System.out.println("出栈的值为："+value); return value;    }    //循环栈元素    public void show(){ if (isEmpty()){     throw new RuntimeException("栈为空，请入栈~~~"); } for (int i = top; i >=0 ; i--) {     System.out.println("a["+i+"]"+"="+stack[i]); }    }    //判断是否为算数符    public static boolean isOperate(char num){ return num=='+'||num=='-'||num=='*'||num=='/';    }    //判断字符串等级，*或/为高等级，+ -为低等级，字符为0    public  int priority(char num){ int result=0; if (num=='+'||num=='-'){     result=-1; }else if (num=='*'||num=='/'){     result=1; }else{     result=0; } return result;    }    //计算数值    public static int cal(int num1,int num2,int character){ int res=0; switch (character){     case '+': res=num1+num2; break;     case '-':  res=num2-num1;  break;     case '*':  res=num1*num2;  break;     case '/':  res=num2/num1;  break;     default:  break; } return res;    }}

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