IO中flush()函數的使用代碼示例

The java.io.Writer.flush() method flushes the stream. If the stream has saved any characters from the various write() methods in a buffer, write them immediately to their intended destination. Then, if that destination is another character or byte stream, flush it. Thus one flush() invocation will flush all the buffers in a chain of Writers and OutputStreams.

 public class Demo {public static void main(String[] ars) throws Exception {System.out.println("hello");PrintWriter writer = new PrintWriter(System.out);writer.println("writer start");// writer.flush();try {Thread.sleep(3000);}catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}writer.println("writer close");writer.close();}}

如上面代碼，如果flush()被註釋掉，則打印完“hello”之後3秒才會打印”writer start”，”writer close”，因為writer.close()在關閉輸出流前會調用一次flush()。效果如下：

如果flush()沒有被註釋掉，則則打印完“hello”之後會立即打印”writer start”。

總結

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