查找有关子网和掩码的信息的 Java 代码出错

Question

我已经编写了一个代码来从 ip 地址输入中查找子网掩码、广播 ID 等。但是，我收到以下错误，并且代码仅部分运行，没有语法错误：

linux@ubuntu:~/Desktop$ javac Subnet.java

linux@ubuntu:~/Desktop$ java Subnet

Enter the ip address:138.101.114.250

IP in Binary is10001010011001010111001011111010

Enter the number of addresses:26

Number of bits reqd for address=5

the subnet mask is=27

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 3

at Subnet.main(Subnet.java:31)

linux@ubuntu:~/Desktop$ ^C

这是代码

import java.util.Scanner;

class Subnet{

public static void main(String args[])

{

Scanner sc=new Scanner(System.in);

System.out.print("Enter the ip address:");

String ip=sc.nextLine();

String split_ip[]=ip.split("\\.");

String split_bip[]=new String[4];

String bip="";

for(int i=0;i<4;i++)

{

split_bip[i]=appendZeros(Integer.toBinaryString(Integer.parseInt(split_ip[i])));

bip+=split_bip[i];

}

System.out.println("IP in Binary is"+bip);

System.out.print("Enter the number of addresses:");

int n = sc.nextInt();

int bits=(int)Math.ceil(Math.log(n)/Math.log(2));

System.out.println("Number of bits reqd for address="+bits);

int mask=32-bits;

System.out.println("the subnet mask is="+mask);

int fbip[]=new int[32];

for (int i=0;i<32;i++)fbip[i]=(int)bip.charAt(i)-48;

for(int i=31;i>31-bits;i--)

fbip[i]&=0;

String fip[]={"","",""};

for(int i=0;i<32;i++)

fip[i/8]=new String(fip[i/8]+fbip[i]);

System.out.print("Subnet address is=");

for(int i=0;i<4;i++){

System.out.print(Integer.parseInt(fip[i],2));

if(i!=3)System.out.print(".");

}

System.out.println();

int lbip[]=new int[32];

for(int i=0;i<32;i++)lbip[i]=(int)bip.charAt(i)-48;

for(int i=31;i>31-bits;i--)

lbip[i]|=1;

String lip[]={"","",""};

for(int i=0;i<32;i++)

lip[i/8]=new String(lip[i/8]+lbip[i]);

System.out.print("Broadcast address is=");

for(int i=0;i<4;i++){

System.out.print(Integer.parseInt(lip[i],2));

if(i!=3)System.out.print(".");

}

System.out.println();

}

static String appendZeros(String s)

{

String temp=new String("00000000");

return temp.substring(s.length())+s;

}

}

这只是一个非常小的错误，但我不知道在哪里。

Answer 1

ArrayIndexOutOfBoundsException 意味着您正在尝试访问数组中不存在的元素，即索引大于最后一个元素索引的元素。String[] someArray = new String[]{"a - index 0", "b - index 1", "c - index 2"};String inexistent = someArray[3]; //This will throw an ArrayIndexOutOfBoundsException since there are only three elements in the array, the last having index 2 (it always starts at 0 = zero-based)你的错误是&nbsp;Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 3at Subnet.main(Subnet.java:31)你应该看看Subnet.java文件的第 31 行，看看你是如何计算数组索引的在该行添加断点并检查数组和计算出的索引肯定会有所帮助

Answer 2

我终于发现了一个小错误：String&nbsp;fip[]={"","",""};它位于完整代码的中间。问题是我提交了 4 个字符串，但在上面的错误代码行中，我只让它需要 3 个，答案是我应该再添加一个括号，所以总共 4 个，如下所示：String&nbsp;fip[]={"","","",""};