Integer.parseint in Java, exception when '+' comes first

Question

Integer.parseInt(\"-1000\"); returns -1000 as the output.

Integer.parseInt(\"+500\"); throws an exception.

How will I be able to re

Answer 1

Try DecimalFormat like with the pattern "+#;-#". It will handle explicit signed parsing. Breakdown of the pattern:

• The first part (before ;) is the positive pattern, it has to start with an + char
• The second part is the negative and has to start with a - char

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Example:

DecimalFormat df = new DecimalFormat("+#;-#");
System.out.println(df.parse("+500"));
System.out.println(df.parse("-500"));

Outputs:

500
-500

Answer 2

The implementation has changed from java 6 to 7. Intger.parseInt("+500") used to Exception till java 6 , but works perfectly fine with java 7

Answer 3

One option is to use Java 7... assuming that behaves as documented:

Parses the string argument as a signed decimal integer. The characters in the string must all be decimal digits, except that the first character may be an ASCII minus sign '-' ('\u002D') to indicate a negative value or an ASCII plus sign '+' ('\u002B') to indicate a positive value.

It looks like this was a new feature introduced into Java 7 though. The JDK 6 docs only indicate that - is handled.

Answer 4

The method is behaving as described in the documentation:

The characters in the string must all be decimal digits, except that the first character may be an ASCII minus sign '-' ('\u002D') to indicate a negative value.

You need to skip the first character if it is a + to do the parse correctly:

if (s.charAt(0) == '+') s = s.substring(1);
int val= Integer.parseInt(s);

Answer 5

public static int parseInt(String s) throws NumberFormatException

Parses the string argument as a signed decimal integer. The characters in the string must all be decimal digits, except that the first character may be an ASCII minus sign '-' ('\u002D') to indicate a negative value. The resulting integer value is returned, exactly as if the argument and the radix 10 were given as arguments to the parseInt(java.lang.String, int) method.

Javadoc

Answer 6

I am using Java 7, and Integer.parseInt("+500"); is not throwing any exception.

The characters in the string must all be decimal digits, except that the first character may be an ASCII minus sign '-' ('\u002D') to indicate a negative value or an ASCII plus sign '+' ('\u002B') to indicate a positive value.

Java 7 documentation for Integer.parseInt(String)