Java中的 PushbackReader markSupported() 方法及示例

Java中PushbackReader类的markSupported()方法用来检查这个PushbackReader是否支持mark()操作。它返回一个布尔值，说明阅读器是否支持标记。

句法：

public boolean markSupported()

参数：此方法不接受任何参数

返回值：此方法返回一个布尔值，它表明此 PushbackReader 是否支持 mark() 操作。如果是 markSupported，则返回 true。否则返回false。

以下方法说明了 markSupported() 方法的工作原理：

方案一：

// Java program to demonstrate
// PushbackReader markSupported() method
  
import java.io.*;
import java.util.*;
  
class GFG {
    public static void main(String[] args)
    {
  
        try {
            // Initializing a StringReader
            // and PushbackReader
            String s = "GeeksForGeeks";
  
            StringReader stringReader
                = new StringReader(s);
            PushbackReader pushbackReader
                = new PushbackReader(stringReader);
  
            // check if the mark() method
            // is supported or not
            System.out.println("Is mark() supported:"
                               + pushbackReader.markSupported());
  
            // Close the stream using markSupported()
            pushbackReader.close();
            System.out.println("Stream Closed.");
        }
        catch (Exception e) {
            System.out.println(e);
        }
    }
}

输出：

Is mark() supported:false
Stream Closed.

方案二：

// Java program to demonstrate
// PushbackReader markSupported() method
  
import java.io.*;
import java.util.*;
  
class GFG {
    public static void main(String[] args)
    {
  
        try {
            // Initializing a StringReader
            // and PushbackReader
            String s = "GFG";
  
            StringReader stringReader
                = new StringReader(s);
            PushbackReader pushbackReader
                = new PushbackReader(stringReader);
  
            // check if the mark() method
            // is supported or not
            System.out.println("Is mark() supported:"
                               + pushbackReader.markSupported());
  
            // Close the stream
            pushbackReader.close();
            System.out.println("Stream Closed.");
        }
        catch (Exception e) {
            System.out.println(e);
        }
    }
}

输出：

Is mark() supported:false
Stream Closed.

参考： https://docs.oracle.com/javase/9/docs/api/ Java/io/PushbackReader.html#markSupported–