why is it？about Integer

[jackyustb]

code as following
...
String s1=Integer.toBinaryString(-1073741824)
System.out.println(s1);
int i2=Integer.parseInt(s1,2);
...
the output is ...
11000000000000000000000000000000
java.lang.NumberFormatException: For input string: "11000000000000000000000000000000"
at java.lang.NumberFormatException.forInputString(Num berFormatException.java:48)
at java.lang.Integer.parseInt(Integer.java:480)
at com.main.Tester.main(Tester.java:18)

what's the matter? how to resolve it?

[r035198x]

code as following
...
String s1=Integer.toBinaryString(-1073741824)
System.out.println(s1);
int i2=Integer.parseInt(s1,2);
...
the output is ...
11000000000000000000000000000000
java.lang.NumberFormatException: For input string: "11000000000000000000000000000000"
at java.lang.NumberFormatException.forInputString(Num berFormatException.java:48)
at java.lang.Integer.parseInt(Integer.java:480)
at com.main.Tester.main(Tester.java:18)

what's the matter? how to resolve it?

11000000000000000000000000000000 is not an int (too big)

The specs say

"An exception of type NumberFormatException is thrown if any of the following situations occurs:

• The first argument is null or is a string of length zero.
• The radix is either smaller than Character.MIN_RADIX or larger than Character.MAX_RADIX.
• Any character of the string is not a digit of the specified radix, except that the first character may be a minus sign '-' ('\u002D') provided that the string is longer than length 1.
• The value represented by the string is not a value of type int. "

[horace1]

as indicated by r035198x the 32-bit binary value 11000000000000000000000000000000
is too large for an int. If you you convert it to a BigInteger, e.g.

String s1=Integer.toBinaryString(-1073741824);
System.out.println(s1.length() + " bits " +s1);
BigInteger bigI = new BigInteger(s1, 2);
System.out.println("Big integer " + bigI);
 

this prints
32 bits 11000000000000000000000000000000
Big integer 3221225472

showing that 3221225472 is larger than 2147483647 the maximum value an int can have

[maverick19]

the reasons why your int value was long because in binary representation(2s complement) the first bit is the sign bit.