推读回读(char，int，int)方法在 Java 中的示例

原文:https://www . geesforgeks . org/puback reader-readchar-int-int-method-in-Java-with-examples/

Java 中 【推回阅读器类】 的 read(char[]，int，int) 方法用于将指定长度的字符读入到指定偏移量的数组中。这个方法阻塞流直到:

  • It takes some input from the stream.
  • Some IOException occurred.
  • It has reached the end of the stream when reading.

语法:

public int read(char[] charArray, 
                     int offset, 
                     int length)

参数:此方法接受三个强制参数:

  • Chararray , which is an array of characters to be written into the stream.
  • Offset is the offset index for writing characters in the array.
  • Length is the number of characters to be written in the array.

返回值:该方法返回一个整数值，即从流中读取的字符数。如果未读取任何字符，则返回-1。

异常:如果输入输出时出现错误，该方法抛出以下异常:

  • Exception: .
  • Index out of bounds exception: If the offset value is not in the character array

的范围内

下面的方法说明了 read(char[]，int，int)方法的工作原理:

程序 1:

// Java program to demonstrate
// PushbackReader read(char, int, int) 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);

            // Get the character array
            // to be read from the stream
            char[] charArray = new char[5];

            // Get the offset index
            int offset = 0;

            // Get the length
            int length = 5;

            // Read the charArray
            // to this reader using read() method
            // This will put the str in the stream
            // till it is read by the reader
            pushbackReader
                .read(charArray, offset, length);

            // Print the read charArray
            System.out.println(
                Arrays.toString(charArray));

            // Close the stream
            pushbackReader.close();
            System.out.println("Stream Closed.");
        }
        catch (Exception e) {
            System.out.println(e);
        }
    }
}

输出:

[G, e, e, k, s]
Stream Closed.

程序二:

// Java program to demonstrate
// PushbackReader read(char, int, int) 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);

            // Get the character array
            // to be read from the stream
            char[] charArray = new char[5];

            // Get the offset index
            int offset = 0;

            // Get the length
            int length = 2;

            // Read the charArray
            // to this reader using read() method
            // This will put the str in the stream
            // till it is read by the reader
            pushbackReader
                .read(charArray, offset, length);

            // Print the read charArray
            System.out.println(
                Arrays.toString(charArray));

            // Close the stream
            pushbackReader.close();
            System.out.println("Stream Closed.");
        }
        catch (Exception e) {
            System.out.println(e);
        }
    }
}

输出:

[G, F,,, ]
Stream Closed.

参考:https://docs . Oracle . com/javase/9/docs/API/Java/io/puback reader . html # read-char:A-int-int-

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