是否可以使用双引号字符作为hashmap键的一部分？

Question

我将有一个像“hello”world这样的字符串作为一个hashmap键。这个键实际上是来自用户输入，这就是为什么有可能把这样的东西作为一个键。这样可以吗？

Answer 1

Absolutely. The double-quote character is only "special" as far as Java source code is concerned. You can even escape it within Java itself:

HashMap<String, String> map = new HashMap<String, String>();
map.put("foo\"bar", "value");
System.out.println(map.get("foo\"bar")); // Will print value

Here the key itself is foo"bar - the backslash is just for escaping within the string literal.

Answer 2

Yes, of course. Even the 0-Character, which often is used as an End-of-String symbol in C is okey in Java, so there are really no constraints.

Answer 3

Sure. If the key is of type String , then all characters are allowed. There is no limitation.

Just a reminder: assuming, the user enters:

 Jack"o"Lantern

then the Java literal is

 "Jack\"o\"Lantern"

Answer 4

As the others told you, strings in java are allowed to contain all unicode characters, so for keys in a hashmap, you're fine.

But be careful when creating SQL queries, http requests or similar using strings which contain unfiltered user input - your software may be open to SQL injection or cross site scripting attacks then. Using mechanisms like prepared statements instead of string concatenation will help in this case.