为什么我得到索引越界异常？ [英] Why am I getting index out of bounds exception?

问题描述

我已经制作了这个代码，将整个基数为10的数字转换成二进制数。我相信的代码是它需要的一切，但我不能让我使用ArrayLists。我花了几个小时在这个网站和其他尝试无数的变化无济于事。我已经得到了没有错误的编译代码但是一旦我输入一个int，程序崩溃了。

这是代码：

  import java.util.Scanner; 
 import java.util.ArrayList; 
 
公共类BinaryConverter {
 public static void main（String [] args）{
 Scanner in = new Scanner（System.in）; 
 ArrayList< Integer> binary = new ArrayList< Integer>（）; 
 int a = in.nextInt（）; 
 binary = binaryConverter（a）; 
 for（int i = binary.size（）; i> -1; i = i  -  1）{
 System.out.print（binary.get（i））; 
} 
} 
 public static ArrayList< Integer> binaryConverter（Integer n）{
 ArrayList< Integer> remainder = new ArrayList< Integer>（）; 
 while（n / 2！= 0）{
 remainder.add（n％2）; 
 n = n / 2; 
} 
 remainder.add（n％2）; 
返还余额; 
} 
} 
  

这些是java输入时抛出的异常一个数字。

  Jons-iMac：java jon $ java BinaryConverter 
 142 
 
异常在线程main中java.lang.IndexOutOfBoundsException：java.base / jdk.internal.util.Preconditions.outOfBounds（Preconditions.java:64）的索引8越界长度为8 
 
 at java.base / jdk.internal.util.Preconditions.outOfBoundsCheckIndex（Preconditions.java:70）
 at java.base / jdk.internal.util.Preconditions.checkIndex（Preconditions.java:248）
 at java.base / java.util.Objects.checkIndex（Objects.java:372）
 at java.base / java.util.ArrayList.get（ArrayList.java:440）
 at BinaryConverter.main （BinaryConverter.java:16）
  

我希望这是足够的信息。

解决方案

在您的代码中，您获取索引值，该值被错误地评估。

  for（int i = binary.size（）;我> -1; i = i  -  1）{
 System.out.print（binary.get（i））; 
} 
  

的分配binary.size（）确实超出范围，因为索引从 binary.size（）计算到零，但它超出了范围，这是从零到 binary.size（） - 1 。

I've made this code to convert whole base 10 numbers into binary. The code I believe is everything that it needs to be but I can't get me ArrayLists to work. I've spent a few hours on this site and other trying countless changes to no avail. I've gotten the code to compile without and errors but as soon as I enter an int the program crashes.

Here is the code:

import java.util.Scanner;
import java.util.ArrayList;

public class BinaryConverter {
   public static void main(String[] args) {
      Scanner in = new Scanner(System.in);
      ArrayList<Integer> binary = new ArrayList<Integer>();
      int a = in.nextInt();
      binary = binaryConverter(a);
      for (int i = binary.size(); i > -1; i = i - 1){
         System.out.print(binary.get(i));
      }
  }
  public static ArrayList<Integer> binaryConverter(Integer n) {
   ArrayList<Integer> remainder = new ArrayList<Integer>();
   while (n/2 != 0) {
      remainder.add(n%2);
      n = n/2;
   }
   remainder.add(n%2);
   return remainder;
  }
}

These are the exceptions java throws at me when I input a number.

Jons-iMac:java jon$ java BinaryConverter
142

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index 8 out-of-bounds for length 8
    at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:64)
    at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:70)
    at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:248)
    at java.base/java.util.Objects.checkIndex(Objects.java:372)
    at java.base/java.util.ArrayList.get(ArrayList.java:440)
    at BinaryConverter.main(BinaryConverter.java:16)

I hope this is enough information.

解决方案

In your code you get the value by index which is evaluated incorrectly.

  for (int i = binary.size(); i > -1; i = i - 1){
     System.out.print(binary.get(i));
  }

Assignment of binary.size() indeed out of bounds, because indexes counted from binary.size() to zero, but it is out of range which is bound from zero to binary.size()-1.

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