Java中的Scanner、BufferedReader 和 StreamTokenizer使用详解

import java.util.Scanner;
public class ScannerExample {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("Enter a string:");
        String inputString = scanner.nextLine();  // 读取一行文本
        System.out.println("You entered: " + inputString);
        System.out.println("Enter an integer:");
        int inputInt = scanner.nextInt();  // 读取整数
        System.out.println("You entered the number: " + inputInt);
        System.out.println("Enter a double:");
        double inputDouble = scanner.nextDouble();  // 读取浮点数
        System.out.println("You entered the double: " + inputDouble);
        scanner.close();
    }
}

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
public class BufferedReaderExample {
    public static void main(String[] args) {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        try {
            System.out.println("Enter a line of text:");
            String input = reader.readLine();  // 读取一行文本
            System.out.println("You entered: " + input);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                reader.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

import java.io.*;
import java.util.*;
public class Main {
    static StreamTokenizer st = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
    public static void main(String[] args) throws IOException {
        int n = nextInt();
    }
    public static int nextInt() throws IOException {
        st.nextToken();
        return (int)st.nval;
    }
}

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
import java.io.StreamTokenizer;
public class StreamTokenizerExample {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        System.out.println("Enter some text:");
        processTokens(reader);  // 处理输入的标记
    }
    /**
     * 处理输入的文本并打印每个标记。
     * @param reader 输入流
     * @throws IOException 读取流时抛出的异常
     */
    public static void processTokens(BufferedReader reader) throws IOException {
        // 创建 StreamTokenizer 对象
        StreamTokenizer tokenizer = new StreamTokenizer(reader);
        // 遍历输入流，处理每个标记
        while (tokenizer.nextToken() != StreamTokenizer.TT_EOF) {
            processTokenByType(tokenizer);  // 根据标记类型处理
        }
    }
    /**
     * 根据不同的标记类型处理输入
     * @param tokenizer StreamTokenizer 对象
     */
    public static void processTokenByType(StreamTokenizer tokenizer) {
        try {
            switch (tokenizer.ttype) {
                case StreamTokenizer.TT_WORD:
                    System.out.println("Word: " + tokenizer.sval);  // 处理单词
                    break;
                case StreamTokenizer.TT_NUMBER:
                    System.out.println("Number: " + tokenizer.nval);  // 处理数字
                    break;
                case StreamTokenizer.TT_EOL:
                    System.out.println("End of line encountered.");  // 处理行结束符
                    break;
                case StreamTokenizer.TT_EOF:
                    // EOF 不需要处理
                    break;
                default:
                    System.out.println("Other: " + (char) tokenizer.ttype);  // 处理其他字符
                    break;
            }
        } catch (IOException e) {
            // 统一抛出异常
            throw new RuntimeException("Error processing the token", e);
        }
    }
}