Java 中的 Reader read()方法，示例

原文:https://www . geesforgeks . org/reader-read-method-in-Java-with-examples/

Java 中 Reader 类的 read() 方法用于从流中读取单个字符。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.

此方法被声明为抽象方法。这意味着，如果需要在读取字符时更改操作，Reader 抽象类的子类应该重写此方法。

语法:

public abstract int read()

参数:该方法不接受任何参数

返回值:该方法返回一个整数值，它是从流中读取的整数值。范围可以从 0 到 65535。否则，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，该方法抛出异常。

下面的方法说明了 read()方法的工作原理:

程序 1:

// Java program to demonstrate
// Reader read() method

import java.io.*;
import java.util.*;

class GFG {
    public static void main(String[] args)
    {

        try {

            String str = "GeeksForGeeks";

            // Create a Reader instance
            Reader reader
                = new StringReader(str);

            // Get the character
            // to be read from the stream
            int ch;

            // Read the first 5 characters
            // to this reader using read() method
            // This will put the str in the stream
            // till it is read by the reader
            for (int i = 0; i < 5; i++) {
                ch = reader.read();
                System.out.println("\nInteger value "
                                   + "of character read: "
                                   + ch);
                System.out.println("Actual "
                                   + "character read: "
                                   + (char)ch);
            }

            reader.close();
        }
        catch (Exception e) {
            System.out.println(e);
        }
    }
}

输出:

Integer value of character read: 71
Actual character read: G

Integer value of character read: 101
Actual character read: e

Integer value of character read: 101
Actual character read: e

Integer value of character read: 107
Actual character read: k

Integer value of character read: 115
Actual character read: s

程序二:

// Java program to demonstrate
// Reader read() method

import java.io.*;
import java.util.*;

class GFG {
    public static void main(String[] args)
    {

        try {
            String str = "GeeksForGeeks";

            // Create a Reader instance
            Reader reader
                = new StringReader(str);

            // Get the character
            // to be read from the stream
            int ch;

            // Read the first character
            // to this reader using read() method
            // This will put the str in the stream
            // till it is read by the reader
            ch = reader.read();
            System.out.println("\nInteger value "
                               + "of character read: "
                               + ch);
            System.out.println("Actual "
                               + "character read: "
                               + (char)ch);

            reader.close();
        }
        catch (Exception e) {
            System.out.println(e);
        }
    }
}

输出:

Integer value of character read: 71
Actual character read: G

参考:https://docs . Oracle . com/javase/9/docs/API/Java/io/reader . html # read–

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