因为你可以从我的尝试中得知,我正在试图弄清楚我是如何创建一个程序,让用户5秒钟输入一些文本行,然后扫描仪将计算多少行进入了。我刚刚开始学习Java作为我的第二语言,所以请尽量简单地解释一切:)
我有两个理论说明为什么它不起作用。第一个是nextLine()将返回整行,无论它是否为空,而不是NL等于“”,它实际上将等于整行(即“”)。我的第二个理论是,我不知道我在做什么,程序流程到处都是。无论如何,这是我的代码:
class OrigClass{
public static void main(String args[]){
Scanner ScanObj = new Scanner(System.in);
int Count = 0;
String NL = ScanObj.nextLine();
try{
Thread.sleep(5000);}
catch (InterruptedException e){
e.printStackTrace();
}
while (!NL.equals("")){
Count++;
NL = ScanObj.nextLine();
}
System.out.print("You Entered " + Count + " Lines.");
ScanObj.close();
}
}
哦,我忘了提到hasNext()是我最初的尝试:
import java.util.Scanner;
class OrigClass{
public static void main(String args[]){
Scanner ScanObj = new Scanner(System.in);
int Count = 0;
try{
Thread.sleep(5000);}
catch (InterruptedException e){
e.printStackTrace();
}
while (ScanObj.hasNext() == true){
Count++;
ScanObj.nextLine();
}
System.out.print("You Entered " + Count + " Lines.");
ScanObj.close();
}
}
答案 0 :(得分:1)
从它的外观来看,这段代码应该可行。我唯一的猜测是你手动输入输入并忘记用CTRL+D
表示输入结束。但是,执行此操作后,如果您不使用NoSuchElementException
,则会获得ScanObj.hasNext()
。
您还可以使用输入重定向运行代码。 java OrigClass < data
更好的方法是:
import java.util.Scanner;
public class Sc {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
int count = 0;
String nl; // = scan.nextLine();
//while (!NL.equals(""))
while(scan.hasNext())
{
count++;
nl = scan.nextLine();
}
System.out.println("Done! Count: " + count);
scan.close();
}
}
这里的不同之处在于我们保存了第一个nextLine()
,直到我们在while循环中。这将准确计算输入中有多少行。
请勿忘记用CTRL+D
发出输入结束信号。
答案 1 :(得分:1)
这个解决方案并不是很好。但是有效。
public class FiveSecond {
public static void main(String args[]){
new Thread(new Count(new Reader())).start();
}
}
class Count implements Runnable{
Reader r;Thread t;
Robot ro;
public Count(Reader t){this.r=t;
try {
ro=new Robot();
} catch (AWTException e) {e.printStackTrace();}
}
@Override
public void run() {
t=new Thread(r);
//t.setDaemon(true); //[S2]
t.start();
try{
Thread.sleep(5000);
}catch(Exception e){}
t.interrupt();
//Implicitly press the enter key in order to release the readLine() method :D
//not recommended, and it's not a good idea, but works
ro.keyPress(KeyEvent.VK_ENTER);
ro.keyRelease(KeyEvent.VK_ENTER);
/*
* this is possible to save the strings lines in somewhere in order to access from invoker application
* or send back the strings by socket, etc . . .
*/
System.out.println("number of entered lines "+r.getCount()+"\n");
//you would run this main as a process and get the number of counts
//System.exit(r.getCount()); //[S2]
}
}
class Reader implements Runnable{
private List<String> lines;
private volatile int count;
private BufferedReader br;
public Reader(){
lines=new ArrayList<String>();
br=new BufferedReader(new InputStreamReader(System.in));
}
@Override
public void run() {
try{String line;
System.out.println("you have 5 second to detect a 2048 length character, then your system will broken");
while((line=br.readLine())!=null){
if(!Thread.currentThread().isInterrupted()){
count++;lines.add(line);}else{break;}
}
//for showing the lines entered
//System.out.println(lines.toString());
}catch(Exception ex){}
}
public int getCount(){return this.count;}
}
但最好的方法是运行一个单独的流程来计算行数,你只需删除[S2]
个注释即可实现它。