Java：charAt 转换为 int？
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Java: charAt convert to int?
提问by sling
I would like to key in my nircnumber e.g. S1234567Iand then put 1234567individualy as a integer as indiv1as charAt(1), indiv2as charAt(2), indivas charAt(3), etc. However, when I use the code below, I can't seem to get even the first number out? Any idea?
我想输入我的nirc号码，例如S1234567I，然后将1234567个人作为整数作为indiv1as charAt(1)、indiv2as charAt(2)、indivascharAt(3)等。但是，当我使用下面的代码时，我似乎无法得到第一个数字？任何的想法？
Scanner console = new Scanner(System.in);
System.out.println("Enter your NRIC number: ");
String nric = console.nextLine();
int indiv1 = nric.charAt(1);
System.out.println(indiv1);
采纳答案by Jon Skeet
You'll be getting 49, 50, 51 etc out - those are the Unicode code points for the characters '1', '2', '3' etc.
您将得到 49、50、51 等 - 这些是字符“1”、“2”、“3”等的 Unicode 代码点。
If you knowthat they'll be Western digits, you can just subtract '0':
如果您知道它们将是西方数字，则只需减去 '0'：
int indiv1 = nric.charAt(1) - '0';
However, you should only do this after you've already validated elsewhere that the string is of the correct format - otherwise you'll end up with spurious data - for example, 'A' would end up returning 17 instead of causing an error.
但是，您应该只在已经在其他地方验证字符串格式正确后才执行此操作 - 否则您最终会得到虚假数据 - 例如，'A' 最终会返回 17 而不是导致错误。
Of course, one option is to take the values and then check that the results are in the range 0-9. An alternative is to use:
当然，一种选择是取值，然后检查结果是否在 0-9 范围内。另一种方法是使用：
int indiv1 = Character.digit(nric.charAt(1), 10);
This will return -1 if the character isn't an appropriate digit.
如果字符不是合适的数字，这将返回 -1。
I'm not sure if this latter approach will cover non-Western digits - the first certainly won't - but it sounds like that won't be a problem in your case.
我不确定后一种方法是否会涵盖非西方数字——第一种肯定不会——但听起来这对你来说不是问题。
回答by jonathanasdf
int indiv1 = Integer.parseInt(nric.charAt(1));
int indiv1 = Integer.parseInt(nric.charAt(1));
回答by Roman
try {
int indiv1 = Integer.parseInt ("" + nric.charAt(1));
System.out.println(indiv1);
} catch (NumberFormatException npe) {
handleException (npe);
}
回答by starblue
Take a look at Character.getNumericValue(ch).
回答by shareef
I know question is about char to int but this worth mentioning because there is negative in char too ))
我知道问题是关于 char 到 int 的，但这值得一提，因为 char 中也有负数））
From JavaHungry you must note the negative numbers for integer if you dont wana use Character.
如果您不想使用字符，则必须从 JavaHungry 中注意整数的负数。
Converting String to Integer : Pseudo Code
将字符串转换为整数：伪代码
1. Start number at 0
2. If the first character is '-'
Set the negative flag
Start scanning with the next character
For each character in the string
Multiply number by 10
Add( digit number - '0' ) to number
If negative flag set
Negate number
Return number
public class StringtoInt {
公共类 StringtoInt {
public static void main (String args[])
{
String convertingString="123456";
System.out.println("String Before Conversion : "+ convertingString);
int output= stringToint( convertingString );
System.out.println("");
System.out.println("");
System.out.println("int value as output "+ output);
System.out.println("");
}
public static int stringToint( String str ){
int i = 0, number = 0;
boolean isNegative = false;
int len = str.length();
if( str.charAt(0) == '-' ){
isNegative = true;
i = 1;
}
while( i < len ){
number *= 10;
number += ( str.charAt(i++) - '0' );
}
if( isNegative )
number = -number;
return number;
}
}
