奇怪的Groovy / Java String比较行为

def a = new HashSet()
def str1 = "str1"
def str2 = "str2"
def b = "$str1-$str2"
def c = "str1-str2"
println "b: $b"
println "c: $c"
println "b.equals(C): " + (b.equals(C))
println "b == c: " + (b == C)
println "b.compareTo(C): " + (b.compareTo(C))

a.add(b)
println "a.contains(C): " + a.contains(C)

使用Groovy 1.8和JDK 1.6.0_14运行时,其输出如下：

b: str1-str2                                                                                                               
c: str1-str2
b.equals(C): false
b == c: true
b.compareTo(C): 0
a.contains(C): false

两个字符串“b”和“c”打印相同的字符序列,但是b.equals(C)是假的.根据JDK 1.6手册,equals()函数应该返回：

为什么equals()不返回上面记录和演示的值？奇怪的是,compareTo()返回0！