ArayIndexOutOfBoundsException不起作用

Question

我的代碼有問題：

import java.io.*;
import java.util.*;
public class goTooFar {
    public static void main(String[] a){

        int i =4;
        int[] ar = new int[i];
        int n = i;
        Scanner sc = new Scanner(System.in);

        System.out.println("Enter the size of an array: ");
        try {
            n = sc.nextInt();
        } catch(ArrayIndexOutOfBoundsException e) {
            System.out.println("Now you have gone too far");
        }


        System.out.println("Enter " + n + " elements of an array: ");
        for (i = 0; i <= n; i++) {
            try {
                ar[i] = sc.nextInt();
            } catch(ArrayIndexOutOfBoundsException e) {
                e.printStackTrace();
                System.out.println("Now you have gone too far");
            }
        System.out.println("Output Numbers: ");
            for (i = 0; i <= n; i++) {
                System.out.println(ar[i]);
            }
        }
    }
}

我有這樣的輸入：

> Enter the size of an array: 
7

> Enter 7 elements of an array: 
1 4 2 5 3 9 0 7

但是，事實證明是這樣的：

>Output Numbers: 
1
0
0
0
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 4
    at goTooFar.main(goTooFar.java:31)

我該怎么做才能解決此問題？ 有人能幫我嗎？ 非常感謝。 :)

Answer 1

您將數組的長度初始化為4：

int i =4;
int[] ar = new int[i];

因此，當您輸入更長的數組長度時，您將獲得ArrayIndexOutOfBoundsException。

您需要從用戶獲取長度后創建數組：

System.out.println("Enter " + n + " elements of an array: ");
ar = new int[n]; // initialize a new array
for(i = 0; i < n; i++){ // n is not a valid index for an array of length n

同時更改另一個循環的范圍

    for(i = 0; i <= n; i++){
        System.out.println(ar[i]);
    }

至

    for(i = 0; i < n; i++){
        System.out.println(ar[i]);
    }

Answer 2

您的問題是這部分for(i = 0; i <= n; i++)

數組以索引0開頭。因此，如果數組的大小類似於您的情況7，則最高索引將為6。（0,1,2,3,4,5,6）

您只需要循環來檢查i < n 。

另外，在向用戶詢問數組的大小之前，已將數組的大小初始化為4。 因此，您需要在輸入發生后使用數組進行初始化

Answer 3

更改

n = sc.nextInt();

至

n = sc.nextInt();
ar = new int[n];

Answer 4

同樣，for循環的輸出應在輸入循環之外System.out.println("Output Numbers: "); for(int i = 0; i <n; i++){ System.out.println(ar[i]); } System.out.println("Output Numbers: "); for(int i = 0; i <n; i++){ System.out.println(ar[i]); } System.out.println("Output Numbers: "); for(int i = 0; i <n; i++){ System.out.println(ar[i]); }最終代碼如下：

   int[] ar = null;
    int n = 0;
    Scanner sc = new Scanner(System.in);

    System.out.println("Enter the size of an array: ");
    try{
        n = sc.nextInt();
    }catch(ArrayIndexOutOfBoundsException e){
        System.out.println("Now you have gone too far");
    }

    ar = new int[n];
    System.out.println("Enter " + n + " elements of an array: ");
    for(int i = 0; i < n; i++){
        try{
            ar[i] = sc.nextInt();
        }catch(ArrayIndexOutOfBoundsException e){
            e.printStackTrace();
            System.out.println("Now you have gone too far");
        }

    }

    System.out.println("Output Numbers: ");
    for(int i = 0; i <n; i++){
        System.out.println(ar[i]);
    }

Answer 5

您的問題已通過此代碼解決...我僅使用您的代碼...

public class goTooFar {

    public static void main(String[] a) {

        int i = 0, n = 0;
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter the size of an array: ");
        n = sc.nextInt();

        int[] ar = new int[n];   // Problem 1 Fixed.

        System.out.println("Enter " + n + " elements of an array: ");
        for (i = 0; i < n; i++) {           // Problem 2 fixed
                ar[i] = sc.nextInt();  // Enhancement 1         
        }
        System.out.println("Output Numbers: ");
        for (i = 0; i < n; i++) {
            System.out.println(ar[i]);
        }
        sc.close(); // Enhancement 2
    }
}

您做錯事的清單...需要修改的地方...

1. 默認情況下，使用4個元素初始化數組，然后要求用戶輸入所需的元素數。

2. 每次for (i = 0; i <= n; i++) ...時都具有n + 1次迭代...而是for (i = 0; i < n; i++) ...

沒問題...增強功能...

1. 除非您正在做**dangerous**否則無需try-catch ...
2. 始終關閉您的資源...這是一個好習慣。

Answer 6

在獲取變量n的值后聲明數組，並將for循環范圍從0更改為<n：

public static void main(String[] args)
{       
    int n = 0 ;
    Scanner sc = new Scanner(System.in);

    System.out.println("Enter the size of an array: ");
    try{
        n = sc.nextInt();
    }catch(ArrayIndexOutOfBoundsException e){
        System.out.println("Now you have gone too far");
    }

    int [] ar = new int[n];  //declare the array after getting input from user about how many numbers will he enter

    System.out.println("Enter " + n + " elements of an array: ");   // change both loops to run from 0 to < n
    for(int i = 0; i < n; i++){
            ar[i] = sc.nextInt();
    }
    System.out.println("Output Numbers: ");
        for(int i = 0; i < n; i++){
            System.out.println(ar[i]);
        }    
}