如何在 java 中使用并行 arrays 打印扫描仪元素？

Question

I am new to learning about parallel arrays and want to know how to effectively print content/elements using parallel array only, I tried but couldn't get it to work and function the way I want.

The task is : The program inputs an integer from the user representing how many peoples' information will be entered. Then, the program inputs the information one person at a time (name first, then age), storing this information in two related arrays.

Next, the program inputs an integer representing the person on the list whose information should be displayed (to get information for the first person, the user would enter '1'). The program makes a statement about the person's name and age.

Although I got the name and age to work until the integer the user inputs, but after that I am not sure how to do

Sample input:

4
Vince
5
Alexina
8
Ahmed
4
Jorge
2
2 // I am confused about this part, how would I make it so that it prints the desired name,
     //for example with this input, it should print:

Sample output:

Alexina is 8 years old

My code:

import java.util.Scanner;

class Example {
  public static void main (String[] args) {

    Scanner keyboard = new Scanner(System.in);

    int[] numbers = new int[keyboard.nextInt()];
    for (int x = 0; x < num.length; x++){
    String[] name = {keyboard.next()};
    int[] age = {keyboard.nextInt()}; 
    }
    int num2 = keyboard.nextInt();
        System.out.println(); // what would I say here?
  }
}

Answer 1

You need to rewrite your code so your arrays aren't being assigned within the loop. You want to add values to the arrays, not reset them each time, and you want to be able to access them afterwards. Below is a modified version of your code:

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

    int num = keyboard.nextInt();
    keyboard.nextLine(); //you also need to consume the newline character(s)
    String[] name = new String[num]; //declare the arrays outside the loop
    int[] age = new int[num]; 
    for (int x = 0; x < num; x++){
        name[x] = keyboard.nextLine(); //add a value instead of resetting the array
        age[x] = keyboard.nextInt();
        keyboard.nextLine(); //again, consume the newline character(s) every time you call nextInt()
    }
    int num2 = keyboard.nextInt() - 1; //subtract one (array indices start at 0)
    System.out.println(name[num2] + " is " + age[num2] + " years old"); //construct your string with your now-visible arrays
}

Answer 2

As I think you have to think about the local and global variable usage in java.In brief, Local variables can only use within the method or block, Local variable is available only to method or block in which it is declared. For example:

{ 
  int y[]=new Int[4];
}

this y array can be accessed within the block only. Global Variable has to be declared anywhere in the class body but not inside any method or block. If a variable is declared as global, it can be used anywhere in the class. In your code you try to create arrays and use them out of the For loop. But your arrays are valid only inside the For loop. After every loop runs all info is lost.there will be new array creation for every iteration of For loop.

therefore, In order to access and save the information you have to declare your arrays before the For loop and access and store data using iteration number as the index. finally, to print the data you gathered, you have to scan new input as integer variable.then you can access your arrays as you wanted.

    //For example 
    int [] age=new int[4]; //global -Can access inside or outside the For loop
    int[] numbers = new int[keyboard.nextInt()];
    for (int x = 0; x < 4; x++){

       age[x] = keyboard.nextInt(); //Local 
    }
    int num2 = keyboard.nextInt();
    System.out.println(age[num2]); // Here you have to access global arrays using num2 num2
  }
}