Exception in thread "main" java.lang.NumberFormatException: For input string: "D437D437" under radix 16

Question

String d="0xD437D437";
System.out.println(Integer.decode(d));

Answer 1

The docs state

This sequence of characters must represent a positive value or a NumberFormatException will be thrown.

But 0xD437D437 is a negative value, namely -734538697, as can be seen by Integer.toHexString(-734538697) resulting in "d437d437".

Therefore either parse it as a Long as @Bonniu says if you are looking for a positive value or if you are actually trying to parse a negative int you could just convert the resulting Long back into an Integer / int:

Long.decode("0xD437D437").intValue() // -734538697

Answer 2

Your number is too big to fit in integer type - 0x7FFFFFFF in hex is the largest number (2147483647 = 2^31-1). If you want to use this String as a number, use Long.decode(d) to get it as Long.

String d = "0x7FFFFFFF";
String e = "0x80000000";
String f = "0xD437D437";
System.out.println(Integer.decode(d));
System.out.println(Long.decode(e));
System.out.println(Long.decode(f));

will print

2147483647
2147483648
3560428599