What happens when you use arithmetic operators inside of a string declaration?

Question

If there is an arithmetic operator inside of a string declaration, how does the String treat the operator?
For example in this case:

String s = "de32";
s = s.charAt(0) * 2 + "";   
System.out.println(s);

String s is not dd but instead is 102 . What is the * 2 mean for the string?

Answer 1

s.charAt(0) is a char ('d'), and char is a numeric type. The numeric value of the character 'd' is 100 . Therefore s.charAt(0) * 2 simply multiplies that value by 2 , which results in 200 (not 102 as you wrote).

Then the result is converted to a String , since you appended to it an empty String , so s is assigned "200" .

The expression is evaluated left to right, so it is equivalent to:

s = (s.charAt(0) * 2) + "";

• First the char 'd' is promoted to an int and multiplied by 2 .
• Then the resulting int (200) is appended to the empty String "". resulting in the String "200".

Answer 2

在0位置，char d在那里并且它乘以2.所以d的ASCII值乘以2.由于d的ASCII值是100所以它给出结果200.然后它被附加到空字符串并给出“200”作为一个字符串。