华为上机测试题（表达式运算-java）

import java.util.Scanner;

public class Calculator {

/* 例如：表达式 3*8+7-2中，dataNum=4，opNum=3 */
private static int daNum = 0;    //表达式中数据个数
private static int opNum = 0;    //表达式中运算符个数

public static void main(String[] args) {

System.out.println("请输入运算表达式（例如：3*8+7-2）:");
Scanner s = new Scanner(System.in);
//String str = s.nextLine().toString();
char[] ch = s.nextLine().toCharArray();
s.close();
StringBuffer sbOP = new StringBuffer();
StringBuffer sbDA = new StringBuffer();

int dataIndex = 0;
int[] data = new int[32];    // 限定能处理的最大数据个数为32

for(int i = 0; i < ch.length; i++)
{
if(('+' == ch[i])||('-' == ch[i])||('*' == ch[i])||('/' == ch[i]))
{
sbOP.append(ch[i]);
opNum++;
for(int j = dataIndex; j < i; j++)
{
sbDA.append(ch[j]);
}
data[daNum++] = Integer.parseInt(sbDA.toString());
sbDA.delete(0, sbDA.length());    //清空sbDA
dataIndex = i+1;
}
}
for(int j = dataIndex; j < ch.length; j++)
{
sbDA.append(ch[j]);
}
data[daNum++] = Integer.parseInt(sbDA.toString());
int[] da = new int[daNum];    //数值数组
for(int i = 0; i < daNum; i++)
{
da[i] = data[i];
//System.out.println("da:"+da[i]);
}
char[] op = sbOP.toString().toCharArray();    //运算符数组

System.out.println("="+cal(da, op));
}

private static int cal(int[] da, char[] op) {

if(1 == daNum)
{
return da[0];
}

// 初始化 标示所以da值都是有效的
boolean[] flag = new boolean[daNum];
for(int i = 0; i < daNum; i++)
{
flag[i] = true;
}

while(1 != daNum)
{
// 乘除运算
for(int i = 0; i < opNum; i++)
{
if('*' == op[i])
{
da[i+1] = da[i] * da[i+1];
flag[i] = false;
daNum--;
}
if('/' == op[i])
{
da[i+1] = da[i] / da[i+1];
flag[i] = false;
daNum--;
}
}

// 加减运算
int index = 0;
for(int i = 0; i < opNum; i++)
{
index = i+1;
if('+' == op[i])
{
while(!flag[index])
{
index++;
}
da[index] = da[i] + da[index];
flag[i] = false;
daNum--;
}
if('-' == op[i])
{
while(!flag[index])
{
index++;
}
da[index] = da[i] - da[index];
flag[i] = false;
daNum--;
}
}
}

return da[opNum];
}
}