String类

用过的一些方法
String substring(int beginIndex)
Returns a string that is a substring of this string.
String substring(int beginIndex, int endIndex)
Returns a string that is a substring of this string.

int lastIndexOf(String str)
Returns the index within this string of the last occurrence of the specified substring. The last occurrence of the empty string "" is considered to occur at the index value this.length().

boolean contains(CharSequence s)
Returns true if and only if this string contains the specified sequence of char values.

boolean startsWith(String prefix)
Tests if this string starts with the specified prefix.

String replace(char oldChar, char newChar)
Returns a string resulting from replacing all occurrences of oldChar in this string with newChar.

boolean matches(String regex)
Tells whether or not this string matches the given regular expression.

引用JAVA8 API文档