Java FilterInputStream available()用法及代碼示例

FilterInputStream類available()方法

• available() 方法可在java.io包。
• available() 方法用於返回可以從此 FilterIputStream 讀取的剩餘可用字節，而不會被此 FilterInputStream 的此方法的下一次調用阻塞。
• available() 方法是一個非靜態方法，它隻能通過類對象訪問，如果我們嘗試使用類名訪問方法，那麽我們將得到一個錯誤。
• available() 方法可能會在返回要讀取的左字節時拋出異常。
  IOException:在執行時遇到任何輸入/輸出錯誤時可能會拋出此異常。

用法:

    public int available();

參數：

• 它不接受任何參數。

返回值：

該方法的返回類型是int，它返回可以讀取的近似可用字節數。

例：

// Java program to demonstrate the example 
// of int available() method of FilterInputStream

import java.io.*;

public class AvailableOfFIS {
 public static void main(String[] args) throws Exception {
  FileInputStream fis_stm = null;
  FilterInputStream fil_stm = null;
  int count = 0;

  try {
   // Instantiates FileInputStream and 
   // FilterInputStream
   fis_stm = new FileInputStream("D:\\includehelp.txt");
   fil_stm = new BufferedInputStream(fis_stm);

   // Loop to read until available
   // bytes left
   while ((count = fil_stm.read()) != -1) {

    // By using available() method is to
    // return the available bytes to be read
    int avail_bytes = fil_stm.available();

    // Display corresponding bytes value
    byte b = (byte) count;

    // Display value of avail_bytes and b
    System.out.print("fil_stm.available():" + avail_bytes);
    System.out.println(":" + "byte:" + b);
   }
  } catch (Exception ex) {
   System.out.println(ex.toString());
  } finally {
   // with the help of this block is to
   // free all necessary resources linked
   // with the stream
   if (fis_stm != null) {
    fis_stm.close();

    if (fil_stm != null) {
     fil_stm.close();
    }
   }
  }
 }
}

輸出

fil_stm.available():15:byte:74
fil_stm.available():14:byte:97
fil_stm.available():13:byte:118
fil_stm.available():12:byte:97
fil_stm.available():11:byte:32
fil_stm.available():10:byte:87
fil_stm.available():9:byte:111
fil_stm.available():8:byte:114
fil_stm.available():7:byte:108
fil_stm.available():6:byte:100
fil_stm.available():5:byte:46
fil_stm.available():4:byte:46
fil_stm.available():3:byte:46
fil_stm.available():2:byte:46
fil_stm.available():1:byte:46
fil_stm.available():0:byte:46