算法四自带类库源码（In）

Posted 2022-02-16 guanhang89

• • In类

学习学习，正好适合初学者

In类

import java.io.BufferedInputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.Socket;
// import java.net.HttpURLConnection;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.InputMismatchException;
import java.util.Locale;
import java.util.NoSuchElementException;
import java.util.Scanner;
import java.util.regex.Pattern;
public final class In 
    private static final String CHARSET_NAME = "UTF-8";
    private static final Locale LOCALE = Locale.US;
    private static final Pattern WHITESPACE_PATTERN
        = Pattern.compile("\\\\pjavaWhitespace+");
    private static final Pattern EMPTY_PATTERN
        = Pattern.compile("");
    private static final Pattern EVERYTHING_PATTERN
        = Pattern.compile("\\\\A");
    private Scanner scanner;
    //System.in通过缓冲流包装了一下
    //然后设定语言环境
    public In() 
        scanner = new Scanner(new BufferedInputStream(System.in), CHARSET_NAME);
        scanner.useLocale(LOCALE);
    
    //从套接字接受输入流
    public In(Socket socket) 
        if (socket == null) throw new NullPointerException("argument is null");
        try 
            InputStream is = socket.getInputStream();
            scanner = new Scanner(new BufferedInputStream(is), CHARSET_NAME);
            scanner.useLocale(LOCALE);
        
        catch (IOException ioe) 
            throw new IllegalArgumentException("Could not open " + socket);
        
    
    //从url接受输入流
    public In(URL url) 
        if (url == null) throw new NullPointerException("argument is null");
        try 
            URLConnection site = url.openConnection();
            InputStream is     = site.getInputStream();
            scanner            = new Scanner(new BufferedInputStream(is), CHARSET_NAME);
            scanner.useLocale(LOCALE);
        
        catch (IOException ioe) 
            throw new IllegalArgumentException("Could not open " + url);
        
    
    //从文件里面接受输入流
    public In(File file) 
        if (file == null) throw new NullPointerException("argument is null");
        try 
            scanner = new Scanner(file, CHARSET_NAME);
            scanner.useLocale(LOCALE);
        
        catch (IOException ioe) 
            throw new IllegalArgumentException("Could not open " + file);
        
    
    //从文件名或者网站名接受输入流，先试读文件，再试读网站
    public In(String name) 
        if (name == null) throw new NullPointerException("argument is null");
        try 
            // first try to read file from local file system
            File file = new File(name);
            if (file.exists()) 
                scanner = new Scanner(file, CHARSET_NAME);
                scanner.useLocale(LOCALE);
                return;
            
            // next try for files included in jar
            URL url = getClass().getResource(name);
            // or URL from web
            if (url == null) 
                url = new URL(name);
            
            URLConnection site = url.openConnection();
            // in order to set User-Agent, replace above line with these two
            // HttpURLConnection site = (HttpURLConnection) url.openConnection();
            // site.addRequestProperty("User-Agent", "Mozilla/4.76");
            InputStream is     = site.getInputStream();
            scanner            = new Scanner(new BufferedInputStream(is), CHARSET_NAME);
            scanner.useLocale(LOCALE);
        
        catch (IOException ioe) 
            throw new IllegalArgumentException("Could not open " + name);
        
    
    public In(Scanner scanner) 
        if (scanner == null) throw new NullPointerException("argument is null");
        this.scanner = scanner;
    
    //一些和Scanner类相关的方法
    public boolean exists()  
        return scanner != null;
    
    public boolean isEmpty() 
        return !scanner.hasNext();
    
    public boolean hasNextLine() 
        return scanner.hasNextLine();
    
    //判断是否还有字符，包括whitespace
    public boolean hasNextChar() 
        scanner.useDelimiter(EMPTY_PATTERN);//换成空字符串分割
        boolean result = scanner.hasNext();
        scanner.useDelimiter(WHITESPACE_PATTERN);//再换回java默认的
        return result;
    
    public String readLine() 
        String line;
        try 
            line = scanner.nextLine();
        
        catch (NoSuchElementException e) 
            line = null;
        
        return line;
    
    public char readChar() 
        scanner.useDelimiter(EMPTY_PATTERN);
        String ch = scanner.next();
        assert ch.length() == 1 : "Internal (Std)In.readChar() error!"
            + " Please contact the authors.";//这里使用了断言
        scanner.useDelimiter(WHITESPACE_PATTERN);
        return ch.charAt(0);
      
    public String readAll() 
        if (!scanner.hasNextLine())
            return "";
        String result = scanner.useDelimiter(EVERYTHING_PATTERN).next();//以字符串开头
        // not that important to reset delimeter, since now scanner is empty
        scanner.useDelimiter(WHITESPACE_PATTERN); // but let's do it anyway
        return result;
    
    public String readString() 
        return scanner.next();
    
    public int readInt() 
        return scanner.nextInt();
    
    public double readDouble() 
        return scanner.nextDouble();
    
    public float readFloat() 
        return scanner.nextFloat();
    
    public long readLong() 
        return scanner.nextLong();
    
    public short readShort() 
        return scanner.nextShort();
    
    public byte readByte() 
        return scanner.nextByte();
    
    //读布尔值
    public boolean readBoolean() 
        String s = readString();
        if (s.equalsIgnoreCase("true"))  return true;
        if (s.equalsIgnoreCase("false")) return false;
        if (s.equals("1"))               return true;
        if (s.equals("0"))               return false;
        throw new InputMismatchException();
    
    public String[] readAllStrings() 
        // we could use readAll.trim().split(), but that's not consistent
        // since trim() uses characters 0x00..0x20 as whitespace
        String[] tokens = WHITESPACE_PATTERN.split(readAll());
        if (tokens.length == 0 || tokens[0].length() > 0)
            return tokens;
        String[] decapitokens = new String[tokens.length-1];//如果第一个字符串长度为0，就切除
        for (int i = 0; i < tokens.length-1; i++)
            decapitokens[i] = tokens[i+1];
        return decapitokens;
    
    public String[] readAllLines() 
        ArrayList<String> lines = new ArrayList<String>();
        while (hasNextLine()) 
            lines.add(readLine());
        
        return lines.toArray(new String[0]);
    
    public int[] readAllInts() 
        String[] fields = readAllStrings();
        int[] vals = new int[fields.length];
        for (int i = 0; i < fields.length; i++)
            vals[i] = Integer.parseInt(fields[i]);
        return vals;
    
    public double[] readAllDoubles() 
        String[] fields = readAllStrings();
        double[] vals = new double[fields.length];
        for (int i = 0; i < fields.length; i++)
            vals[i] = Double.parseDouble(fields[i]);
        return vals;
    
    public void close() 
        scanner.close();