在Scala中你只须要使用==就能够判断字符串相等,而不须要像Java同样须要使用的equals方法来判断。java
scala> val s1 = "hello" s1: String = hello scala> val s2 = "hello" s2: String = hello scala> val s3 = "h" + "ello" s3: String = hello scala> s1 == s2 res4: Boolean = true scala> s1 == s3 res5: Boolean = true
使用==判断字符串相等的好处是,能够避免空指针异常。即==左边的字符串是空,也能够正常判断。es6
scala> val s4 = null s4: Null = null scala> s4 == s3 res6: Boolean = false scala> s3 == s4 res7: Boolean = false
忽略大小写来比较两个字符串是否一致,有两个方法:一个是把两个字符串都转化为大写或者小写再比较,另外一个是直接使用equalsIgnoreCase方法。ide
scala> val s1 = "hello" s1: String = hello scala> val s2 = "Hello" s2: String = Hello scala> s1.toUpperCase == s2.toUpperCase res8: Boolean = true scala> s1.equalsIgnoreCase(s2) res9: Boolean = true
须要注意的是,使用以上两个方法的时候,"."号左边的字符串不能为空。es5
scala> val s4: String = null s4: String = null scala> s4.equalsIgnoreCase(s2) java.lang.NullPointerException ... 32 elided scala> s4.toUpperCase == s2.toUpperCase java.lang.NullPointerException ... 32 elided
Scala中的==定义在AnyRef类中,在Scala API文档中的解释为。x == that:首先判断x是否为空,若是x为空而后判断that是否为空,若是x不为空那么调用x.equals(that)来判断是否相等。scala