Question

Java关于IP地址的程序

IP addresses are made up of four numbers, each between 0 and 255 separated by a period. For example, 128.253.21.58 is an IP address.
Write a program to enter four numbers and test if they make up a valid IP address. In other words, test to see if the numbers entered are between 0 and 255 inclusive.

Sample Run 1:
Please enter the first octet:898
Please enter the second octet:34
Please enter the third octet:712
Please enter the fourth octet:45
Octet 1 is incorrect
Octet 3 is incorrect

Sample Run 2:
Please enter the first octet::112
Please enter the second octet:200
Please enter the third octet:0
Please enter the fourth octet:254
IP Address: 112.200.0.254

ip地址有4个0-255的数字组成，比如1.3.2.255
怎么写一个程序让用户输入
4个整数，如果有一个大于255或者小于0，就print 第几个错了
如果都没错就print ip地址。
例子1：
第1次输入：1
第2次输入：2
第3次输入：3
第4次输入：4
输出：1.2.3.4
例子2：
第1次输入：1
第2次输入：255
第3次输入：3
第4次输入：4
输出：第二个错误

我写的，但是不正确，求支出错误

public static void main(String[] args)
{
Scanner scan = new Scanner(System.in);
System.out.println("Please enter 4 inter from 0 to 255");
int a = scan.nextInt();
int b = scan.nextInt();
int c = scan.nextInt();
int d = scan.nextInt();
if (a>=0&&a<=255)
{
if( b>=0&&d<=255)
{
if (c>=0&&d<=255)
{
if (d>=0&&d<=255)
{
System.out.print(a+"."+b+"."+c+"."+d);
}
else
{
System.out.print("test 4 is not valid");
}
}
else
{
System.out.print("test 3 is not valid");
}
}else
{
System.out.print("test 2 is not valid");
}
}
else
{
System.out.print("test 1 is not valid");
}
上文中的例子2错的。应该是

例子2：
第1次输入：1
第2次输入：256
第3次输入：3
第4次输入：4
输出：第二个错误

Answer 1

if( b>=0&&d<=255)
{
if (c>=0&&d<=255)
{
if (d>=0&&d<=255)
{
System.out.print(a+"."+b+"."+c+"."+d);这里后面判断的都是d,改成：
if( b>=0&&b<=255)
{
if (c>=0&&c<=255)
{
if (d>=0&&d<=255)
{
System.out.print(a+"."+b+"."+c+"."+d);就行