为什么条件表达式使用第二个 if 语句而不是 else if 工作？

Question

Input: 1 2 7 3 4 7 3 2 7

This works if I replace the else if statement with an if statement

Correct Output: Max number 7 and most occurrence is 3

This does not work with the else if statement

Wrong output: Max number 7 and most occurrence is 2

import java.util.Scanner;

public class App {
    public static void main(String[] args) throws Exception {
        Scanner input = new Scanner(System.in);
        System.out.print("Enter numbers: ");
        String str = input.nextLine();
        int num = Integer.parseInt(str.substring(0, str.indexOf(" ")));
        int max = num;
        int index = str.indexOf(" ");
        int count = 0;
        for (int i = 1; i < str.length() - 1; i++) {
            str = str.substring(index + 1);
            index = str.indexOf(" ");
            if (index != -1) {
                num = Integer.parseInt(str.substring(0, index));
                if (num > max) {
                    max = num;
                    count = 1;
                }
                else if (num == max) { // change this to if statement with same expression it works
                    count++;
                }
            }
        }
        System.out.printf("Max number %d and most occurence is %d", max, count);
    }
}

Answer 1

I added a println statement just after you set num each time through the loop:

num = Integer.parseInt(str.substring(0, index));
System.out.println("num: " + num);   // <-- added this

Then ran the program with your input:

Enter numbers: 1 2 7 3 4 7 3 2 7
num: 2
num: 7
num: 3
num: 4
num: 7
Max number 7 and most occurence is 2

Instead of seeing nine occurrences of "num: x" printed, it shows only five. I didn't track down which specific part of your code has the issue, but there are a few suspicious looking bits, namely:

• Using str.length() in the for loop condition while also setting str to something new within the body of the for loop
• Various calls to indexOf() and substring(), not sure which of them is correct or not – the code is complicated to follow

---

Here's a variation that uses a StringTokenizer to separate each part of the input string. This isn't perfect (negative numbers won't work, and anything other than numeric input will throw an exception in Integer.parseInt()), but it's a simple example that's easy to follow and should get you going.

System.out.print("Enter numbers: ");
StringTokenizer tokenizer = new StringTokenizer(new Scanner(System.in).nextLine());

int num = 0, max = 0, count = 0;
while (tokenizer.hasMoreTokens()) {
    String token = tokenizer.nextToken();
    num = Integer.parseInt(token);
    if (num > max) {
        max = num;
        count = 1;
    } else if (num == max) {
        count++;
    }
}

System.out.printf("Max number %d and most occurence is %d", max, count);

Here's the output:

Enter numbers: 1 2 7 3 4 7 3 2 7
Max number 7 and most occurence is 3

Answer 2

Your code for getting every number is so complicated. Instead use method split of String class

public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.print("Enter numbers: ");
        String str = input.nextLine();
        String[] numbers = str.split(" ");
        for(int i = 0; i < numbers.length; i++) {
            //Do your business logic
        }
    }

Answer 3

the machine can run inside multiple if statement if they are arranged in same level, but can not run inside the else if / else statement if the first if meet the condition

# if a is greater than 100, then it will print 1, 10, 100
if (a > 1){print 1}
if (a > 10) {print 10}
if (a > 100) {print 100}

# if a is greater than 100, then it will only print 1, and it will exit the if /else if / else check
if (a > 1){print 1}
else if (a > 10) {print 10}
else (a > 100) {print 100}

probably it is for this reason, that at certain conditions, the same thing happened at the else if statement

Answer 4

change else if to if statement still wrong, like this paramaters 1 2 7 3 4 7 3 2 7 8 8 8

public static void main(String[] args) throws Exception {
    Scanner input = new Scanner(System.in);
    System.out.print("Enter numbers: ");
    String str = input.nextLine();
    String[] array = str.split(" ");
    int max = Integer.MIN_VALUE, num;
    int count = 0;
    for (int i = 0; i < array.length; i++) {
        num = Integer.parseInt(array[i]);
        if (num > max) {
            max = num;
            count = 1;
        } else if (num == max) { // change this to if statement with same expression it works
            count++;
        }
    }
    System.out.printf("Max number %d and most occurence is %d", max, count);
}