Java:如何从System.console()获取输入

Question

我试图使用Console类来获取用户的输入,但是当我调用时会返回一个null对象System.console().在使用System.console之前,我是否必须更改任何内容？

Console co=System.console();
System.out.println(co);
try{
    String s=co.readLine();
}

Answer 1

使用Console读取输入(仅在IDE外部可用):

System.out.print("Enter something:");
String input = System.console().readLine();

另一种方式(无处不在):

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Test {
    public static void main(String[] args) throws IOException { 
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        System.out.print("Enter String");
        String s = br.readLine();
        System.out.print("Enter Integer:");
        try {
            int i = Integer.parseInt(br.readLine());
        } catch(NumberFormatException nfe) {
            System.err.println("Invalid Format!");
        }
    }
}

System.console()在IDE中返回null,
因此如果您确实需要使用System.console(),请从McDowell中读取此解决方案.

Answer 2

Scanner in = new Scanner(System.in);

int i = in.nextInt();
String s = in.next();

Answer 3

从控制台/键盘读取输入字符串的方法很少.以下示例代码显示如何使用Java从控制台/键盘读取字符串.

public class ConsoleReadingDemo {

public static void main(String[] args) {

    // ====
    BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
    System.out.print("Please enter user name : ");
    String username = null;
    try {
        username = reader.readLine();
    } catch (IOException e) {
        e.printStackTrace();
    }
    System.out.println("You entered : " + username);

    // ===== In Java 5, Java.util,Scanner is used for this purpose.
    Scanner in = new Scanner(System.in);
    System.out.print("Please enter user name : ");
    username = in.nextLine();      
    System.out.println("You entered : " + username);


    // ====== Java 6
    Console console = System.console();
    username = console.readLine("Please enter user name : ");   
    System.out.println("You entered : " + username);

}
}

代码的最后一部分使用了java.io.Console类.System.console()在通过Eclipse运行演示代码时,无法获取Console实例.因为eclipse将您的应用程序作为后台进程运行,而不是作为具有系统控制台的顶级进程运行.

Answer 4

这取决于您的环境.javaw例如,如果您正在运行Swing UI ,则无法显示控制台.如果您在IDE中运行,它将在很大程度上取决于特定IDE对控制台IO的处理.

从命令行来看,它应该没问题.样品:

import java.io.Console;

public class Test {

    public static void main(String[] args) throws Exception {
        Console console = System.console();
        if (console == null) {
            System.out.println("Unable to fetch console");
            return;
        }
        String line = console.readLine();
        console.printf("I saw this line: %s", line);
    }
}

运行这个只是java:

> javac Test.java
> java Test
Foo  <---- entered by the user
I saw this line: Foo    <---- program output

另一个选择是使用System.in,您可能想要包装在BufferedReader读取行中,或使用Scanner(再次包装System.in).

Answer 5

在这里找到一些关于从控制台读取的好答案,这里使用"扫描仪"从控制台读取的另一种方式:

import java.util.Scanner;
String data;

Scanner scanInput = new Scanner(System.in);
data= scanInput.nextLine();

scanInput.close();            
System.out.println(data);

Answer 6

尝试这个。希望这会有所帮助。

    String cls0;
    String cls1;

    Scanner in = new Scanner(System.in);  
    System.out.println("Enter a string");  
    cls0 = in.nextLine();  

    System.out.println("Enter a string");  
    cls1 = in.nextLine(); 

Answer 7

使用System.in

http://www.java-tips.org/java-se-tips/java.util/how-to-read-input-from-console.html