Question

HashMap<Character, Character> charMap = new HashMap<Character ,Character>();
charMap['{'] = '}';
charMap['['] = ']';
charMap['('] = ')';

//println charMap.keySet()
Character ch = '{'
println charMap.keySet().contains(ch)

它只是打印错误，而很明显我的设置包含＆＃39; {＆＃34;，任何想法为什么会发生这种情况？（我正在使用groovy进行测试......）

感谢。

Answer 1

'{'是一个字符串，而不是groovy中的字符。为了证明这一点，只需在最后一行打印：

println charMap.keySet()*.class

必须明确地将其类型化为字符：

HashMap<Character, Character> charMap = new HashMap<Character ,Character>();
charMap['{' as char] = '}';
charMap['['] = ']';
charMap['('] = ')';

//println charMap.keySet()
Character ch = '{'
println charMap.keySet().contains(ch)

这是它的工作原理：

//String
assert 'a'.class == String

//Character
def c1= 'a' as char, c2= (char)'b' 
def c3= new Character(c2), c4= c2.charValue()
[c1, c2, c3, c4].each { assert it.class == Character }
assert c2 == c3 && c1 != c2
assert c1 < c2 && c1.compareTo(c2) == -1
assert c2.toString().class == String

jvm中的Set.contains（）不适用于Character类

1 个答案: