java charsequence是什么，讓我們一起了解一下？

CharSequence類是java.lang包下的一個接口，此接口對多種不同的對char訪問的統一接口，像String、StringBuffer、StringBuilder類都是CharSequence的子接口。

那么CharSequence接口是如何實現的？

CharSequence接口的源碼如下：

package?java.lang;
/**
?*?A?CharSequence?is?a?readable?sequence?of?char?values.?This
?*?interface?provides?uniform,?read-only?access?to?many?different?kinds?of
?*?char?sequences.
?*?A?char?value?represents?a?character?in?the?Basic
?*?Multilingual?Plane?(BMP)?or?a?surrogate.?Refer?to?Unicode?Character?Representation?for?details.
?*
?*?
?This?interface?does?not?refine?the?general?contracts?of?the?{@link
?*?java.lang.Object#equals(java.lang.Object)?equals}?and?{@link
?*?java.lang.Object#hashCode()?hashCode}?methods.??The?result?of?comparing?two
?*?objects?that?implement?CharSequence?is?therefore,?in?general,
?*?undefined.??Each?object?may?be?implemented?by?a?different?class,?and?there
?*?is?no?guarantee?that?each?class?will?be?capable?of?testing?its?instances
?*?for?equality?with?those?of?the?other.??It?is?therefore?inappropriate?to?use
?*?arbitrary?CharSequence?instances?as?elements?in?a?set?or?as?keys?in
?*?a?map.?
?*
?*?@author?Mike?McCloskey
?*?@since?1.4
?*?@spec?JSR-51
?*/
public?interface?CharSequence?{
????/**
?????*?Returns?the?length?of?this?character?sequence.??The?length?is?the?number
?????*?of?16-bit?chars?in?the?sequence.

?????*
?????*?@return??the?number?of?chars?in?this?sequence
?????*/
????int?length();
????/**
?????*?Returns?the?char?value?at?the?specified?index.??An?index?ranges?from?zero
?????*?to?length()?-?1.??The?first?char?value?of?the?sequence?is?at
?????*?index?zero,?the?next?at?index?one,?and?so?on,?as?for?array
?????*?indexing.?

?????*
?????*?
If?the?char?value?specified?by?the?index?is?a
?????*?surrogate,?the?surrogate
?????*?value?is?returned.
?????*
?????*?@param???index???the?index?of?the?char?value?to?be?returned
?????*
?????*?@return??the?specified?char?value
?????*
?????*?@throws??IndexOutOfBoundsException
?????*??????????if?the?index?argument?is?negative?or?not?less?than
?????*??????????length()
?????*/
????char?charAt(int?index);
????/**
?????*?Returns?a?new?CharSequence?that?is?a?subsequence?of?this?sequence.
?????*?The?subsequence?starts?with?the?char?value?at?the?specified?index?and
?????*?ends?with?the?char?value?at?index?end?-?1.??The?length
?????*?(in?chars)?of?the
?????*?returned?sequence?is?end?-?start,?so?if?start?==?end
?????*?then?an?empty?sequence?is?returned.?
?????*
?????*?@param???start???the?start?index,?inclusive
?????*?@param???end?????the?end?index,?exclusive
?????*
?????*?@return??the?specified?subsequence
?????*
?????*?@throws??IndexOutOfBoundsException
?????*??????????if?start?or?end?are?negative,
?????*??????????if?end?is?greater?than?length(),
?????*??????????or?if?start?is?greater?than?end
?????*/
????CharSequence?subSequence(int?start,?int?end);
????/**
?????*?Returns?a?string?containing?the?characters?in?this?sequence?in?the?same
?????*?order?as?this?sequence.??The?length?of?the?string?will?be?the?length?of
?????*?this?sequence.?

?????*
?????*?@return??a?string?consisting?of?exactly?this?sequence?of?characters
?????*/
????public?String?toString();
}

另外CharSequence類是一個描述字符串的一個描述型接口，有三個類實現了該接口，分別為：String、StringBuffer、StringBuilder類，所以說，看到這個類，就直接當做是一個字符串類型就可以了，示例代碼如下：

/**
?*?String、Stringbuffer、StringBuilder?三個字符相關的類都實現
?*??????了CharSequence?類，所以說，以后見到CharSequence描述的就是字符串
?*/
?
public?class?CharSequenceStudy?{
????public?static?void?main(String[]?args)?{
????????CharSequence?str?=?"www.ayit.com";
????????CharSequence?sub?=?str.subSequence(4,8);
????????System.out.println(sub);
????????System.out.println(str.length());
????}
}

拓展一下：對于抽象類或者接口來說不可以直接使用new的方式創建對象，但是可以直接給它賦值； CharSequence b = "s"; > 。CharSequence b = "s" 是一個類型強轉操作，等于CharSequence b = (CharSequence) new String("s")。

以上就是小編今天的分享了，希望可以幫助到大家。