将Unicode字符串“ \\ u0063”转换为“ c”

Question

I'm doing some cryptoanalysis homework and was trying to write code that does a + b = c. My idea was to use unicode. b +(ba) = c. Problem is my code returns a the unicode value of c not the String "c" and I can't convert it.

Please can someone explain the difference between the string below called unicode and those called test and test2? Also is there any way I could get the string unicodeOfC to print "c"?

//this calculates the unicode value for c
String unicodeOfC = ("\\u" + Integer.toHexString('b'+('b'-'a') | 0x10000).substring(1));

//this prints \u0063
System.out.println(unicodeOfC);

String test = "\u0063";

//this prints c
System.out.println(test);

//this is false
System.out.println(test.equals(unicodeOfC));

String test2 = "\u0063";
//this is true
System.out.println(test.equals(test2));

Answer 1

There is no difference between test and test2 . They are both String literals referring to the same String . This String literal is made up of a unicode escape .

A compiler for the Java programming language ("Java compiler") first recognizes Unicode escapes in its input, translating the ASCII characters \\u\u003c/code> followed by four hexadecimal digits to the UTF-16 code unit (§3.1) for the indicated hexadecimal value , and passing all other characters unchanged.

So the compiler will translate this unicode escape and convert it to the corresponding UTF-16 code unit. That is, the unicode escape \c translates to the character c .

In this

String unicodeOfC = ("\\u" + Integer.toHexString('b'+('b'-'a') | 0x10000).substring(1));

the String literal "\\\\u\u0026quot; (which uses a \\ character to escape a \\ character) has a runtime value of \\u\u003c/code> , ie. the two character \\ and u . That String is concatenated with the result of invoking toHexString(..) . You then invoke substring on the resulting String and assign its result to unicodeOfC . So the String value is \c , ie. the 6 characters \\ , u , 0 , 0 , 6 , and 3 .

Also is there any way I could get the string unicodeOfC to print "c"?

Similarly to how you created it, you need to get the numerical part of the unicode escape,

String numerical = unicodeOfC.replace("\\u", "");
int val = Integer.parseInt(numerical, 16);
System.out.println((char) val);

You can then print it out.

Answer 2

I think you're not understanding how string escaping works.

In Java backslash is an escape character that allows you to use characters in strings like newlines \\n , tabs \\t , or unicode \c .

Suppose I am writing code and I need to print a newline. I would do this System.out.println("\\n");

Now lets say I want to show a backslash, System.out.println("\\"); will be a compile error but System.out.println("\\\\"); will print \\ .

So your first string is printing the literal backslash character then the letter u then the hexadecimal number.