Is the char literal '\“' the same as '”' ?(backslash-doublequote vs only-doublequote)

问题

Is there's any difference between char literals '\"' and '"' ?

回答1:

There is absolutely no difference. The two char are ==.

System.out.println('\"' == '"'); // prints "true"

Strictly speaking it's not necessary to escape a double quote in a char literal, but it doesn't change this fact that \" denotes the double quote character \u0022.

References

JLS 3.10.6 Escape Sequences for Character and String Literals

`String` analog

We also have the analogous situation for String literals:

System.out.println("\'".equals("'")); // prints "true"

In fact, we can even go a step further and use == for reference equality:

System.out.println("\'" == "'"); // prints "true"

The second snippet proves that the two string literals are really equal, and therefore subject to string interning at compile-time.

References

JLS 3.10.5 String Literals

String literals --or, more generally, strings that are the values of constant expressions-- are "interned" so as to share unique instances, using the method String.intern.

Summary

A single-quote in a char literal MUST be escaped
- Because char literal is quoted in single-quotes
A double-quote in a String literal MUST be escaped
- Because String literal is quoted in double-quotes
It doesn't hurt to escape, even when it's not necessary
- Go with what's most readable