解析存储为字符串的浮点数应抛出异常 [英] Parsing float stored as string should throw Exception
问题描述
我有一个存储号码的字符串。现在我想解析该字符串并获得浮点数。
I have a string which stores a number. Now i want to parse that string and get as float.
import java.util.*;
import java.lang.*;
import java.io.*;
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
public static void main (String[] args) throws java.lang.Exception
{
try {
System.out.println(Integer.parseInt(" 2 "));
} catch(NumberFormatException e) {
System.out.println("Exception caught");
}
System.out.println(Float.parseFloat(" 2.4 "));
}
}
现在在上面的代码中如果你运行它会成功的。我的问题是为什么在整数的情况下尾随空格抛出一个 NumberFormatException
,而解析一个浮点数并不抛出一个?
Now in the above code if you run it it will be successfull. My QUESTION is this why does trailing spaces in case of integer throws a NumberFormatException
while parsing a float doesnt throw one ?
PS:booolean和double解析的情况相同。
PS: Same is the case with booolean and double parsing.
PPS:为什么java中存在不一致?我已经检查了源代码
PPS: Why is there an inconsistency in java ? And i already check the source code
推荐答案
正如您在相关源代码中看到的那样,该值将被修剪:
As you can see in the related source code, the value will be trimmed:
static FloatingDecimal.ASCIIToBinaryConverter readJavaFormatString(String arg) throws NumberFormatException {
boolean arg0 = false;
boolean arg1 = false;
try {
arg = arg.trim();
....
因此在转换为floatValue之前将删除空白。
有关更多信息,请参阅 FloatingDecimal ,由 Float.class
调用。
So the blanks will be removed before converting to a floatValue.
For more informations see the sourcecode of FloatingDecimal which is called by Float.class
.
Integer.parseInt()
不要修剪字符串值:
public static int parseInt(String arg, int arg0) throws NumberFormatException {
if (arg == null) {
throw new NumberFormatException("null");
} else if (arg0 < 2) {
throw new NumberFormatException("radix " + arg0 + " less than Character.MIN_RADIX");
} else if (arg0 > 36) {
throw new NumberFormatException("radix " + arg0 + " greater than Character.MAX_RADIX");
} else {
int arg1 = 0;
boolean arg2 = false;
int arg3 = 0;
int arg4 = arg.length();
int arg5 = -2147483647;
if (arg4 > 0) {
char arg8 = arg.charAt(0);
if (arg8 < 48) {
if (arg8 == 45) {
arg2 = true;
arg5 = MIN_VALUE;
} else if (arg8 != 43) {
throw NumberFormatException.forInputString(arg);
}
if (arg4 == 1) {
throw NumberFormatException.forInputString(arg);
}
++arg3;
}
int arg7;
for (int arg6 = arg5 / arg0; arg3 < arg4; arg1 -= arg7) {
arg7 = Character.digit(arg.charAt(arg3++), arg0);
if (arg7 < 0) {
throw NumberFormatException.forInputString(arg);
}
if (arg1 < arg6) {
throw NumberFormatException.forInputString(arg);
}
arg1 *= arg0;
if (arg1 < arg5 + arg7) {
throw NumberFormatException.forInputString(arg);
}
}
return arg2 ? arg1 : -arg1;
} else {
throw NumberFormatException.forInputString(arg);
}
}
}
这就是为什么你得到一个例外那里
Thats why you get an Exception there
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