怎么返回String类型的啊. 我这样返回不对吗 - 科蚪实务学堂2019春季 - Vijos

问答
lichengjie LV 6 @ 2019-06-10 16:38:24

import java.util.Scanner;

public class 计算机 {
    public static String[] jieguo(String[] shuzi) {
        Scanner in = new Scanner(System.in);
   // int zhi=Integer.parseInt(shuzi[0]);
        
        int chang = in.nextInt();
        int b=0;
        for(int i=0;i<chang;i++) {
            if(shuzi[i].equals("*")) {
                b=Integer.parseInt(shuzi[i-1]) *Integer.parseInt(shuzi[i+1]);
                String s=Integer.toString(b);
                String xin[]=new String [chang-2];
         
                for(int j=0;j<i-1;j++) {
                    xin[j]=shuzi[j-1];
                    xin[i]=s;
                }
                for(int n=i+2;n<xin.length;n++) {
                
                    xin[n]=shuzi[n+2];
                }
            }
            
        }return xin;
    }

lichengjie LV 6 @ 2019-06-10 20:01:42

错误信息是这样的：

3
1 + 2 * 3
Exception in thread "main" java.lang.NumberFormatException: null
at java.base/java.lang.Integer.parseInt(Integer.java:620)
at java.base/java.lang.Integer.parseInt(Integer.java:776)
at 李成杰.计算机.jia(计算机.java:40)
at 李成杰.计算机.zonghe(计算机.java:48)
at 李成杰.计算机.main(计算机.java:54)

小熊 (wlnirvana) LV 8 MOD @ 2019-06-10 17:50:54

你看了函数7.1节视频吗？做笔记了吗？

lichengjie LV 6 @ 2019-06-10 19:34:01

刚又看了一遍

lichengjie LV 6 @ 2019-06-10 20:01:04

import java.util.Scanner;
/*找到第一个乘号的位置*/
public class 计算机 {
    public static int weizhi(String[] a) {
        for (int i = 0; i < a.length; i++) {
            if (a[i] == "*") {
                return i;
            } 
            }
            return 0;
    }
/*创建乘完后的新数组*/
    public static String[] jieguo(String[] shuzi) {
        int chen = weizhi(shuzi);
        if (chen != 0) {

            int a = 0;
            String[] xin = new String[shuzi.length - 2];
            a = Integer.parseInt(shuzi[chen + 1]) * Integer.parseInt(shuzi[chen - 1]);
            String s1 = String.valueOf(a);
            for (int i = 0; i < chen - 1; i++) {
                xin[i] = shuzi[i];
            }
            xin[chen - 1] = s1;
            for (int i = chen + 2; i < xin.length; i++) {
                xin[i] = shuzi[i + 2];
            }
            return jieguo(xin);
        } else {
            return shuzi;
        }

    }
    /*剩下的加法*/
    public static int  jia(String[] abc) {
        int zhi=0;
        for (int i =0;i<abc.length;i+=2) {
            zhi=zhi+Integer.parseInt(abc[i]);
        }
        return zhi;
    }
/*先乘后加*/
    public static int zonghe(String[]suan) {
        String[]m =new String[suan.length];
        m=jieguo(suan);
        return jia(m);
    }
    /*调用总函数*/
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        String []a=new String [n];
        zonghe(a);
    }
}