为什么 Integer.valueOf 无法将十六进制字符串解析回 integer

Question

Why did the following code not work

System.out.println(Integer.valueOf(Integer.toOctalString(-1), 8));
System.out.println(Integer.valueOf(Integer.toBinaryString(-1), 2));
System.out.println(Integer.valueOf(Integer.toHexString(-1), 16));

Answer 1

If you read the documentation , ie the javadoc of Integer.toOctalString(int i) , you will find:

Returns a string representation of the integer argument as an unsigned integer in base 8.

[...]

The value of the argument can be recovered from the returned string s by calling Integer.parseUnsignedInt(s, 8) .

Javadoc of Integer.toBinaryString(int i) and Integer.toHexString(int i) says exactly the same thing, except the base is of course different ( 2 and 16 , respectively).

System.out.println(Integer.parseUnsignedInt(Integer.toOctalString(-1), 8));
System.out.println(Integer.parseUnsignedInt(Integer.toBinaryString(-1), 2));
System.out.println(Integer.parseUnsignedInt(Integer.toHexString(-1), 16));

Output

-1
-1
-1