Hey there! Let's fix up your code step by step—you're already off to a great start with the input logic, but the output section is the main pain point right now since it's hardcoded for only 5 students. Let's break down the issues and build a better version together.

First, Let's Spot the Problems in Your Current Code #

• Redundant Scanner instances: You don't need two Scanner objects—one is enough to handle all input. Using multiple can cause weird bugs with leftover newline characters in the input buffer.
• Broken, hardcoded output: Your final loop is using a for-each loop incorrectly (it will repeat the entire 5-student block studentValue times!) and relies on fixed indexes like arraylist[0]. This will crash if you enter fewer than 5 students, and ignore any students beyond the 5th.
• Unclear variable names: Names like arraylist and ageinput don't clearly describe what they hold. Also, using a char for your loop counter (count) works technically, but it's semantically wrong—counters should be int types.

Here's the Fixed & Optimized Code #

This version works for any number of students, cleans up the input logic, and makes the output dynamic:

import java.util.Scanner;

public class StudentInfo {
    public static void main(String[] args) { 
        // Use a single Scanner for all input operations
        Scanner input = new Scanner(System.in); 

        // Get the number of students from the user
        System.out.print("Number of Students > "); 
        int numStudents = input.nextInt();
        input.nextLine(); // Consume the leftover newline after nextInt()

        // Initialize arrays with clear, descriptive names
        String[] studentNames = new String[numStudents]; 
        int[] studentAges = new int[numStudents]; 

        // Loop to collect each student's details
        for (int i = 0; i < numStudents; i++) { 
            System.out.println("\nEnter details for Student #" + (i + 1)); 
            System.out.println("------------------------------------"); 
            
            System.out.print("Name: "); 
            studentNames[i] = input.nextLine(); // Allows full names (e.g., "Maria Garcia")
            
            System.out.print("Age: "); 
            studentAges[i] = input.nextInt(); 
            input.nextLine(); // Clear the newline buffer before next input
        } 

        // Dynamic output: print exactly as many students as were entered
        System.out.println("\n--- Student Information Summary ---");
        for (int i = 0; i < numStudents; i++) { 
            System.out.println("\nStudent #" + (i + 1)); 
            System.out.println("Name: " + studentNames[i]); 
            System.out.println("Age: " + studentAges[i]); 
        } 

        input.close(); // Clean up the Scanner resource
    }
}

Key Improvements Explained #

• Single Scanner, cleaner input: We use one Scanner and add input.nextLine() after nextInt() to fix a common bug where leftover newlines would skip name inputs.
• Dynamic output: The final loop uses the numStudents variable to iterate exactly as many times as there are students—no more hardcoded indexes!
• Better user experience: Prompts now show "Student #1", "Student #2", etc., and nextLine() lets users enter full names instead of just single words.
• Cleaner code structure: Descriptive variable names make the code easier to read and maintain.

Bonus: An Object-Oriented Upgrade (For Future Learning) #

If you want to make your code even more organized (especially if you add more student details later), you can create a Student class to group name and age together:

import java.util.Scanner;

// Encapsulate student data in a class
class Student {
    private String name;
    private int age;

    public Student(String name, int age) {
        this.name = name;
        this.age = age;
    }

    // Getters to access private fields
    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }
}

public class StudentInfoOO {
    public static void main(String[] args) { 
        Scanner input = new Scanner(System.in); 

        System.out.print("Number of Students > "); 
        int numStudents = input.nextInt();
        input.nextLine();

        // Use an array of Student objects instead of two separate arrays
        Student[] students = new Student[numStudents];

        for (int i = 0; i < numStudents; i++) { 
            System.out.println("\nEnter details for Student #" + (i + 1)); 
            System.out.print("Name: "); 
            String name = input.nextLine(); 
            System.out.print("Age: "); 
            int age = input.nextInt(); 
            input.nextLine();

            // Create and store a new Student object
            students[i] = new Student(name, age);
        } 

        System.out.println("\n--- Student Information Summary ---");
        for (int i = 0; i < numStudents; i++) { 
            Student student = students[i];
            System.out.println("\nStudent #" + (i + 1)); 
            System.out.println("Name: " + student.getName()); 
            System.out.println("Age: " + student.getAge()); 
        } 

        input.close();
    }
}

This approach keeps related data together, making it easier to add more features (like student IDs or grades) later.

内容的提问来源于stack exchange，提问作者Rio Ablas