针对在java中读取System.in的权限和java读取这两个问题，本篇文章进行了详细的解答，同时本文还将给你拓展java–使用控制台为Intellij读取System.in、Java不使用Scan

针对在java中读取System.in的权限和java 读取这两个问题，本篇文章进行了详细的解答，同时本文还将给你拓展java – 使用控制台为Intellij读取System.in、Java 不使用Scanner读取System.in输入流(自己实现一个InputReader)、Java 关闭链接到System.in的扫描仪、java 标准输出与标准错误 out与 err 区别 用法 联系 java中的out与err区别 System.out和System.err的区别 System.out.println...等相关知识，希望可以帮助到你。

• 在java中读取System.in的权限（java 读取）
• java – 使用控制台为Intellij读取System.in
• Java 不使用Scanner读取System.in输入流(自己实现一个InputReader)
• Java 关闭链接到System.in的扫描仪
• java 标准输出与标准错误 out与 err 区别 用法 联系 java中的out与err区别 System.out和System.err的区别 System.out.println...

在java中读取System.in的权限（java 读取）

Console console = System.console();
String input = console.readLine();

grant codeBase "file:/myjar.jar" {
   permission java.security.AllPermission;
};

permission java.lang.RuntimePermission "readFileDescriptor";
permission java.lang.RuntimePermission "writeFileDescriptor";

java – 使用控制台为Intellij读取System.in

public class BasicAssertions {
       @Test
       public void testAssertions(){
           System.out.println("Enter: ");
           Scanner reader = new Scanner(system.in);
           int first = reader.nextInt();
           int second = reader.nextInt();
           String s = reader.next();
           String s2 = reader.next();
           assertTrue(first<=second);
           assertFalse(first+second >100);
           assertNotEquals(s,s2);
           assertNotNull(s2);    
       }    
   }

Java 不使用Scanner读取System.in输入流(自己实现一个InputReader)

StringTokenizer

效率高于split()

构造方法

public StringTokenizer(String str,String delim,boolean returnTokens);

public StringTokenizer(String str,String delim);

public StringTokenizer(String str);

常用方法

int countTokens():返回nextToken方法被调用的次数

boolean hasMoreTokens():返回是否还有分隔符

boolean hasMoreElements():返回是否还有分隔符

String nextToken():返回从当前位置到下一个分隔符的字符串

Object nextElement():返回从当前位置到下一个分隔符的字符串

String nextToken(String delim):与4类似，以指定的分隔符返回结果

InputReader

源码

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

class InputReader {
    private final static int BUF_SZ = 65536;
    private BufferedReader in;
    private StringTokenizer tokenizer;

    InputReader(InputStream buf) {
        this.in = new BufferedReader(new InputStreamReader(buf), BUF_SZ);
        tokenizer = new StringTokenizer("");
    }

    private String next() {
        while (!tokenizer.hasMoreTokens()) {
            try {
                tokenizer = new StringTokenizer(in.readLine());
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        return tokenizer.nextToken().trim();
    }

    int nextInt() {
        return Integer.parseInt(next());
    }

    double nextDouble() {
        return Double.parseDouble(next());
    }
}

使用方法

public class Main {
    public static void main(String[] args) {
        // write your code here
        var cin = new InputReader(System.in);
        System.out.println(cin.nextInt());
        System.out.println(cin.nextDouble());
    }
}

Sample Input

10010 10086.1

Sample Output

10010
10086.1

Java 关闭链接到System.in的扫描仪

/**
     * The "standard" output stream. This stream is already
     * open and ready to accept output data. Typically this stream
     * corresponds to display output or another output destination
     * specified by the host environment or user.
     * <p>
     * For simple stand-alone Java applications, a typical way to write
     * a line of output data is:
     * <blockquote><pre>
     *     System.out.println(data)
     * </pre></blockquote>
     * <p>
     * See the <code>println</code> methods in class <code>PrintStream</code>.
     *
     * @see     java.io.PrintStream#println()
     * @see     java.io.PrintStream#println(boolean)
     * @see     java.io.PrintStream#println(char)
     * @see     java.io.PrintStream#println(char[])
     * @see     java.io.PrintStream#println(double)
     * @see     java.io.PrintStream#println(float)
     * @see     java.io.PrintStream#println(int)
     * @see     java.io.PrintStream#println(long)
     * @see     java.io.PrintStream#println(java.lang.Object)
     * @see     java.io.PrintStream#println(java.lang.String)
     */
    public static final PrintStream out = null;

    /**
     * The "standard" error output stream. This stream is already
     * open and ready to accept output data.
     * <p>
     * Typically this stream corresponds to display output or another
     * output destination specified by the host environment or user. By
     * convention, this output stream is used to display error messages
     * or other information that should come to the immediate attention
     * of a user even if the principal output stream, the value of the
     * variable <code>out</code>, has been redirected to a file or other
     * destination that is typically not continuously monitored.
     */
    public static final PrintStream err = null;

System.setOut(new PrintStream(new FileOutputStream(new File( "d://out.txt "))));
System.setErr(new PrintStream(new FileOutputStream(new File( "d://err.txt "))));