blocks|key|1293413|text|您可以尝试"boolean+ready()“方法。从Java6API文档中可以看出：“如果缓冲区不为空，或者底层字符流准备就绪，则缓冲的字符流已准备就绪。”|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1293414|BufferedReader+r+=+new+BufferedReader(reader);
if(r.ready())
{
+++r.read();
}|code-block|syntax|javascript|1293415|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

You can try the "boolean ready()" method.
From the Java 6 API doc: "A buffered character stream is ready if the buffer is not empty, or if the underlying character stream is ready."

<pre><code>BufferedReader r = new BufferedReader(reader);
if(r.ready())
{
 r.read();
}
</code></pre>

blocks|key|1078507|text|您可以使用PushbackReader。使用它，您可以读取一个字符，然后将其取消读取。这本质上允许您将其推回。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1078508|PushbackReader+pr+=+new+PushbackReader(reader);
char+c+=+(char)pr.read();
//+do+something+to+look+at+c
pr.unread((int)c);+//pushes+the+character+back+into+the+buffer|code-block|syntax|javascript|1078509|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.oracle.com/javase/7/docs/api/java/io/PushbackReader.html^0|5|E|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

You can use a <a href="http://docs.oracle.com/javase/7/docs/api/java/io/PushbackReader.html" rel="noreferrer">PushbackReader</a>. Using that you can read a character, then unread it. This essentially allows you to push it back.

<pre><code>PushbackReader pr = new PushbackReader(reader);
char c = (char)pr.read();
// do something to look at c
pr.unread((int)c); //pushes the character back into the buffer
</code></pre>

blocks|key|1293344|text|下面的代码将查看Stream中的第一个字节。应该可以让你先睹为快。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1293345|BufferedReader+bReader+=+new+BufferedReader(inputStream);
bReader.mark(1);
int+byte1+=+bReader.read();
bReader.reset();|code-block|syntax|javascript|1293346|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

The following code will look at the first byte in the Stream. Should act as a peek for you.

<pre><code>BufferedReader bReader = new BufferedReader(inputStream);
bReader.mark(1);
int byte1 = bReader.read();
bReader.reset();
</code></pre>

blocks|key|1293511|text|通常的习惯用法是，如果BufferedReader#readLine()没有返回null，就会在循环中进行检查。如果到达流的末尾(例如，文件结束、套接字关闭等)，则它返回null。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1293512|例如。|1293513|BufferedReader+reader+=+new+BufferedReader(someReaderSource);
String+line+=+null;
while+((line+=+reader.readLine())+!=+null)+{
++++//+...
}|code-block|syntax|javascript|1293514|如果你不想读入行(顺便说一下，这是选择BufferedReader的主要原因)，那么改用BufferedReader#ready()：|1293515|BufferedReader+reader+=+new+BufferedReader(someReaderSource);
while+(reader.ready())+{
++++int+data+=+reader.read();
++++//+...
}|1293516|entityMap|0|LINK|mutability|MUTABLE|url|http://java.sun.com/javase/6/docs/api/java/io/BufferedReader.html#readLine%2528%2529|1|http://java.sun.com/javase/6/docs/api/java/io/BufferedReader.html#ready%2528%2529^0|B|P|14|4|2D|4|B|P|0|0|0|0|J|E|18|M|18|M|1|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]|$9|15|A|16|B|C]]|D|@$9|17|A|18|1|19]]|E|$]]|$1|F|3|G|5|6|7|1A|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|1B|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|1C|8|@$9|1D|A|1E|B|C]|$9|1F|A|1G|B|C]]|D|@$9|1H|A|1I|1|1J]]|E|$]]|$1|O|3|P|5|J|7|1K|8|@]|D|@]|E|$K|L]]|$1|Q|3|-4|5|6|7|1L|8|@]|D|@]|E|$]]]|R|$S|$5|T|U|V|E|$W|X]]|Y|$5|T|U|V|E|$W|Z]]]]

The normal idiom is to check in a loop if <a href="http://java.sun.com/javase/6/docs/api/java/io/BufferedReader.html#readLine%28%29" rel="nofollow noreferrer"><code>BufferedReader#readLine()</code></a> doesn't return <code>null</code>. If end of stream is reached (e.g. end of file, socket closed, etc), then it returns <code>null</code>.

E.g.

<pre><code>BufferedReader reader = new BufferedReader(someReaderSource);
String line = null;
while ((line = reader.readLine()) != null) {
 // ...
}
</code></pre>

If you don't want to read in lines (which is by the way the major reason a <code>BufferedReader</code> is been chosen), then use <a href="http://java.sun.com/javase/6/docs/api/java/io/BufferedReader.html#ready%28%29" rel="nofollow noreferrer"><code>BufferedReader#ready()</code></a> instead:

<pre><code>BufferedReader reader = new BufferedReader(someReaderSource);
while (reader.ready()) {
 int data = reader.read();
 // ...
}
</code></pre>

blocks|key|1293361|text|BufferedReader+br+=+new+BufferedReader(reader);
br.mark(1);
int+firstByte+=+br.read();
br.reset();|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1293362|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>BufferedReader br = new BufferedReader(reader);
br.mark(1);
int firstByte = br.read();
br.reset();
</code></pre>

blocks|key|1078618|text|您可以使用PushBackReader读取一个字符，然后将其“推回”。这样你就可以肯定地知道有什么东西在那里，而不会影响它的整体状态--一个“窥视”。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1078619|entityMap|0|LINK|mutability|MUTABLE|url|http://java.sun.com/javase/6/docs/api/java/io/PushbackReader.html^0|5|E|5|E|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]]|D|@$9|Q|A|R|1|S]]|E|$]]|$1|F|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]]]

You could use a <a href="http://java.sun.com/javase/6/docs/api/java/io/PushbackReader.html" rel="nofollow noreferrer"><code>PushBackReader</code></a> to read a character, and then "push it back". That way you know for sure that something was there, without affecting its overall state - a "peek".

blocks|key|1078671|text|我的解决方案是..扩展BufferedReader，使用queue作为buf，就可以在queue中使用peek方法。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1078672|public+class+PeekBufferedReader+extends+BufferedReader{

++++private+Queue<String>+++++++buf;
++++private+int+++++++++++++++++bufSize;

++++public+PeekBufferedReader(Reader+reader,+int+bufSize)+throws+IOException+{
++++++++super(reader);
++++++++this.bufSize+=+bufSize;
++++++++buf+=+Queues.newArrayBlockingQueue(bufSize);
++++}

++++/**
+++++*+readAheadLimit+is+set+to+1048576.+Line+which+has+length+over+readAheadLimit+
+++++*+will+cause+IOException.
+++++*+@throws+IOException+
+++++**/
++++//public+String+peekLine()+throws+IOException+{
++++//++super.mark(1048576);
++++//++String+peekedLine+=+super.readLine();
++++//++super.reset();
++++//++return+peekedLine;
++++//}

++++/**
+++++*+This+method+can+be+implemented+by+mark+and+reset+methods.+But+performance+of+
+++++*+this+implementation+is+better+(+about+2times)+than+using+mark+and+reset++
+++++**/
++++public+String+peekLine()+throws+IOException+{
++++++++if+(buf.isEmpty())+{
++++++++++++while+(buf.size()+<+bufSize)+{
++++++++++++++++String+readLine+=+super.readLine();
++++++++++++++++if+(readLine+==+null)+{
++++++++++++++++++++break;
++++++++++++++++}+else+{
++++++++++++++++++++buf.add(readLine);
++++++++++++++++}
++++++++++++}
++++++++}+else+{
++++++++++++return+buf.peek();
++++++++}
++++++++if+(buf.isEmpty())+{
++++++++++++return+null;
++++++++}+else+{
++++++++++++return+buf.peek();
++++++++}
++++}

++++public+String+readLine()+throws+IOException+{
++++++++if+(buf.isEmpty())+{
++++++++++++while+(buf.size()+<+bufSize)+{
++++++++++++++++String+readLine+=+super.readLine();
++++++++++++++++if+(readLine+==+null)+{
++++++++++++++++++++break;
++++++++++++++++}+else+{
++++++++++++++++++++buf.add(readLine);
++++++++++++++++}
++++++++++++}
++++++++}+else+{
++++++++++++return+buf.poll();
++++++++}
++++++++if+(buf.isEmpty())+{
++++++++++++return+null;
++++++++}+else+{
++++++++++++return+buf.poll();
++++++++}
++++}
++++public+boolean+isEmpty()+throws+IOException+{
++++++++if+(buf.isEmpty())+{
++++++++++++while+(buf.size()+<+bufSize)+{
++++++++++++++++String+readLine+=+super.readLine();
++++++++++++++++if+(readLine+==+null)+{
++++++++++++++++++++break;
++++++++++++++++}+else+{
++++++++++++++++++++buf.add(readLine);
++++++++++++++++}
++++++++++++}
++++++++}+else+{
++++++++++++return+false;
++++++++}
++++++++if+(buf.isEmpty())+{
++++++++++++return+true;
++++++++}+else+{
++++++++++++return+false;
++++++++}
++++}
}|code-block|syntax|javascript|1078673|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

my solution was.. extending BufferedReader and use queue as buf, then you can use peek method in queue.

<pre><code>public class PeekBufferedReader extends BufferedReader{

 private Queue&lt;String&gt; buf;
 private int bufSize;

 public PeekBufferedReader(Reader reader, int bufSize) throws IOException {
 super(reader);
 this.bufSize = bufSize;
 buf = Queues.newArrayBlockingQueue(bufSize);
 }

 /**
 * readAheadLimit is set to 1048576. Line which has length over readAheadLimit 
 * will cause IOException.
 * @throws IOException 
 **/
 //public String peekLine() throws IOException {
 // super.mark(1048576);
 // String peekedLine = super.readLine();
 // super.reset();
 // return peekedLine;
 //}

 /**
 * This method can be implemented by mark and reset methods. But performance of 
 * this implementation is better ( about 2times) than using mark and reset 
 **/
 public String peekLine() throws IOException {
 if (buf.isEmpty()) {
 while (buf.size() &lt; bufSize) {
 String readLine = super.readLine();
 if (readLine == null) {
 break;
 } else {
 buf.add(readLine);
 }
 }
 } else {
 return buf.peek();
 }
 if (buf.isEmpty()) {
 return null;
 } else {
 return buf.peek();
 }
 }

 public String readLine() throws IOException {
 if (buf.isEmpty()) {
 while (buf.size() &lt; bufSize) {
 String readLine = super.readLine();
 if (readLine == null) {
 break;
 } else {
 buf.add(readLine);
 }
 }
 } else {
 return buf.poll();
 }
 if (buf.isEmpty()) {
 return null;
 } else {
 return buf.poll();
 }
 }
 public boolean isEmpty() throws IOException {
 if (buf.isEmpty()) {
 while (buf.size() &lt; bufSize) {
 String readLine = super.readLine();
 if (readLine == null) {
 break;
 } else {
 buf.add(readLine);
 }
 }
 } else {
 return false;
 }
 if (buf.isEmpty()) {
 return true;
 } else {
 return false;
 }
 }
}
</code></pre>

Is there a way to check if in <code>BufferedReader</code> object is something to read? Something like C++ <code>cin.peek()</code>. Thanks.

Can I peek on a BufferedReader?

有没有办法检查BufferedReader对象中是否有需要读取的内容？就像C++ cin.peek()一样。谢谢。

问我能偷看一下BufferedReader吗？
EN

回答 7

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问我能偷看一下BufferedReader吗？EN

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问我能偷看一下BufferedReader吗？
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