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("\\p{javaWhitespace}+");
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();
}