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I tried the java language using netbeans 12 with jdk version 8, but it always got an error in the output [duplicate]

I am trying to use Console class to get input from user but a null object is returned when I call System.console(). Do I have to change anything before using System.console?
Console co=System.console();
System.out.println(co);
try{
String s=co.readLine();
}

Using Console to read input (usable only outside of an IDE):
System.out.print("Enter something:");
String input = System.console().readLine();
Another way (works everywhere):
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() returns null in an IDE.
So if you really need to use System.console(), read this solution from McDowell.

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

There are few ways to read input string from your console/keyboard. The following sample code shows how to read a string from the console/keyboard by using Java.
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);
}
}
The last part of code used java.io.Console class. you can not get Console instance from System.console() when running the demo code through Eclipse. Because eclipse runs your application as a background process and not as a top-level process with a system console.

It will depend on your environment. If you're running a Swing UI via javaw for example, then there isn't a console to display. If you're running within an IDE, it will very much depend on the specific IDE's handling of console IO.
From the command line, it should be fine though. Sample:
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);
}
}
Run this just with java:
> javac Test.java
> java Test
Foo <---- entered by the user
I saw this line: Foo <---- program output
Another option is to use System.in, which you may want to wrap in a BufferedReader to read lines, or use Scanner (again wrapping System.in).

Found some good answer here regarding reading from console, here another way use 'Scanner' to read from console:
import java.util.Scanner;
String data;
Scanner scanInput = new Scanner(System.in);
data= scanInput.nextLine();
scanInput.close();
System.out.println(data);

Try this. hope this will help.
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();

The following takes athspk's answer and makes it into one that loops continually until the user types "exit". I've also written a followup answer where I've taken this code and made it testable.
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class LoopingConsoleInputExample {
public static final String EXIT_COMMAND = "exit";
public static void main(final String[] args) throws IOException {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
System.out.println("Enter some text, or '" + EXIT_COMMAND + "' to quit");
while (true) {
System.out.print("> ");
String input = br.readLine();
System.out.println(input);
if (input.length() == EXIT_COMMAND.length() && input.toLowerCase().equals(EXIT_COMMAND)) {
System.out.println("Exiting.");
return;
}
System.out.println("...response goes here...");
}
}
}
Example output:
Enter some text, or 'exit' to quit
> one
one
...response goes here...
> two
two
...response goes here...
> three
three
...response goes here...
> exit
exit
Exiting.

I wrote the Text-IO library, which can deal with the problem of System.console() being null when running an application from within an IDE.
It introduces an abstraction layer similar to the one proposed by McDowell.
If System.console() returns null, the library switches to a Swing-based console.
In addition, Text-IO has a series of useful features:
supports reading values with various data types.
allows masking the input when reading sensitive data.
allows selecting a value from a list.
allows specifying constraints on the input values (format patterns, value ranges, length constraints etc.).
Usage example:
TextIO textIO = TextIoFactory.getTextIO();
String user = textIO.newStringInputReader()
.withDefaultValue("admin")
.read("Username");
String password = textIO.newStringInputReader()
.withMinLength(6)
.withInputMasking(true)
.read("Password");
int age = textIO.newIntInputReader()
.withMinVal(13)
.read("Age");
Month month = textIO.newEnumInputReader(Month.class)
.read("What month were you born in?");
textIO.getTextTerminal().println("User " + user + " is " + age + " years old, " +
"was born in " + month + " and has the password " + password + ".");
In this image you can see the above code running in a Swing-based console.

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

Java Scanner Error : java.util.NoSuchElementException: No line found -- java.base/java.util.Scanner.nextLine(Scanner.java:1651))

I am a beginner with java and programmin over all, So this the full code for a file reader program that counts words or displays text file content, I wanted to take user inputs for commands that I indicated using an if statement, but String printFileCommand = scan.nextLine(); is not working due to the error addressed below:
package com;
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class FileReader {
public static void main(String[] args) throws FileNotFoundException {
Scanner scanTwo = new Scanner(System.in);
System.out.println("Please Enter Your File Path");
String filePath = scanTwo.nextLine();
scanTwo.close();
File fileInput = new File(filePath);
Scanner fileScanner = new Scanner(fileInput);
System.out.println(fileScanner.nextLine());
fileScanner.close();
System.out.println("Commands: PRINT.FILE --> Prints all file COUNT.WORDS --> Counts all words");
System.out.println("Type Command:");
Scanner scan = new Scanner(System.in);
String printFileCommand = scan.nextLine(); <----ERROR HERE
scan.close();
if (printFileCommand.contains("PRINT.FILE")) {
while (fileScanner.hasNextLine()) {
System.out.println(fileScanner.nextLine());
}
} else if (printFileCommand.contains("COUNT.WORDS")) {
int wordCount = 0;
while (fileScanner.hasNext()) {
String fileWords = fileScanner.next();
wordCount++;
// System.out.println(wordCount);
}
System.out.println(wordCount);
}
else {
System.out.println("COMMAND INVALID!");
}
}
}
```
**Terminal Output:**
PS C:\Users\DR\Desktop\FIRST REAL PROGRAMMING> c:; cd 'c:\Users\DR\Desktop\FIRST REAL PROGRAMMING'; & 'c:\Users\DR\.vscode\extensions\vscjava.vscode-java-debug-0.30.0\scripts\launcher.bat' 'C:\Program Files\AdoptOpenJDK\jdk-15.0.1.9-hotspot\bin\java.exe' '--enable-preview' '-XX:+ShowCodeDetailsInExceptionMessages' '-Dfile.encoding=UTF-8' '-cp' 'C:\Users\DR\AppData\Roaming\Code\User\workspaceStorage\458dc35931a3067a355426e5ceeeee32\redhat.java\jdt_ws\FIRST REAL PROGRAMMING_e263b9bc\bin' 'com.FileReader'
Please Enter Your File Path
E://texttwo.txt
This is my text file.
Commands: PRINT.FILE --> Prints all file COUNT.WORDS --> Counts all words
Type Command:
Exception in thread "main" java.util.NoSuchElementException: No line found
at java.base/java.util.Scanner.nextLine(Scanner.java:1651)
at com.FileReader.main(FileReader.java:21)
PS C:\Users\DR\Desktop\FIRST REAL PROGRAMMING>
So why is `String printFileCommand = scan.nextLine();` not working? I tried alot, but its not working...

It doesn't work because your stream for System.in is closed.
You can check it for example System.out.println(System.in.available()); and you will see:
Exception in thread "main" java.io.IOException: Stream closed
at java.io.BufferedInputStream.getInIfOpen(BufferedInputStream.java:159)
at java.io.BufferedInputStream.available(BufferedInputStream.java:410)
you closed it in line: scanTwo.close();

I'm still trying to understand Java myself, but I think you don't exactly need to create and use multiple Scanners to collect data. Since you are searching for strings for the file creations, you could technically do something like:
Scanner scanner = new Scanner(System.in);
String filePath = scanner.nextLine();
With some of the other scanners you can keep since you're specifically calling the fileInputs within the Scanner, but when asking the user for data, I suggest using only one scanner source, but having something like the last line of code I shared as a template for updating your code! If I misunderstood something you're more than welcome to let me know. Thanks!

Please check this question:
NoSuchElementException - class Scanner
Your code will work if you remove the code:
scanTwo.close();
Or removing better:
Scanner scan = new Scanner(System.in);
And use scanTwo for reading (but you don't have to close the scanner with scanTwo.close()).
But I recommend you to read those answers to understand how it works.

Scanner and validating answers like a dictionary in Java

I just wanted to practice my java so I made sort of a dictionary.
But I can't get my code to work on the console. Like it doesn't give me any error, it's just that my console in eclipse won't pop up and when I remove the scanner parts it will pop up. Any help is appreciated! Code:
public static void main(String[] args) {
HeleLijst lijst = new HeleLijst();
Scanner sc = new Scanner(System.in);
String input = sc.nextLine();
System.out.println("Geef een afkorting op: ");
lijst.all();
if (lijst.betekenislist.containsKey(input)) {
System.out.println("De betekenis van " + input + " is: " + lijst.betekenislist.get(input));
} else {
System.out.println("Geen correcte afkorting!");
}
sc.close();
}

The console is waiting for your input... You probably should have printed some kind of message signifying what the input is for

Searching a list of names in a text file from user input

I'm currently in an Introductory Java class at University and I'm having a bit of trouble. Last semester we started with Python and I became very acquainted with it and I would say I am proficient now in writing Python; yet Java is another story. Things are alot different. Anyway, Here is my current assignment: I need to write a class to search through a text document (passed as an argument) for a name that is inputted by the user and output whether or not the name is in the list. The first line of the text document is the amount of names in the list.
The text document:
14
Christian
Vincent
Joseph
Usman
Andrew
James
Ali
Narain
Chengjun
Marvin
Frank
Jason
Reza
David
And my code:
import java.util.*;
import java.io.*;
public class DbLookup{
public static void main(String[]args) throws IOException{
File inputDataFile = new File(args[0]);
Scanner stdin = new Scanner(System.in);
Scanner inFile = new Scanner(inputDataFile);
int length = inFile.nextInt();
String names[] = new String[length];
for(int i=0;i<length;i++){
names[i] = inFile.nextLine();
}
System.out.println("Please enter a name that you would like to search for: ");
while(stdin.hasNext()){
System.out.println("Please enter a name that you would like to search for: ");
String input = stdin.next();
for(int i = 0;i<length;i++){
if(input.equalsIgnoreCase(names[i])){
System.out.println("We found "+names[i]+" in our database!");
break;
}else{
continue;
}
}
}
}
}
I am just not getting the output I am expecting and I cannot figure out why.

Try this
You should trim() your values as they have extra spaces
if(input.trim().equalsIgnoreCase(names[i].trim()))
I have run your example it runs perfectly after using trim(), you have missed to trim()

Create a seperate scanner class to read line by line.You can use BufferedReader also.
final Scanner scanner = new Scanner(file);
while (scanner.hasNextLine()) {
final String str= scanner.nextLine();
if(str.contains(name)) {
// Found the input word
System.out.println("I found " +name+ " in file " +file.getName());
break;
}
}

If you use Java 8:
String[] names;
try (Stream<String> stream = Files.lines(Paths.get(fileName))) {
names = stream.skip(1).toArray(size -> new String[size]);
} catch (IOException e) {
e.printStackTrace();
}

Searching for a string in a text file using Java

I am trying to make the user input an Airport Name, and the program will search from a text file to get the matching Code, right now I only need it to read the line. I have looked into many similar questions in here, but nothing works for me. The program return the else result rather than the found result.
This is my code so far
public static void main (String[] args) throws IOException
{
File file = new File("codes01.dat");
Scanner myFile = new Scanner(file);
Scanner kb = new Scanner(System.in);
String line;
System.out.println("Hey man, this is totally leigt, just enter an Airport code and I'll hook you up.");
System.out.print("First, y'all need to give me the file name: ");
String fileName = kb.nextLine();
if (fileName.equalsIgnoreCase("codes01"))
{
System.out.print("Cool, now give me your Airport Name: ");
String AirportName = kb.nextLine();
while (myFile.hasNextLine())
{
line = myFile.nextLine();
String name = myFile.next();
System.out.println(line);
if(name.equalsIgnoreCase(AirportName))
{
System.out.println("IT'S WORKING, I DON'T KNOW HOW BUT IT IS "+line);
break;
}
else
{
System.out.println("Sorry, dude, ain't no airport in my VERY limited list with that name");
break;
}
}
}

The program return the else result rather than the found result.
That is because you are breaking out of the loop after testing the first line in your file.
Look carefully at your code ... in context.
if(name.equalsIgnoreCase(AirportName)) {
System.out.println("It is working");
break;
} else {
System.out.println("Sorry");
break; // What????
}

Why are you using the break statement in the if-else block? Try to get rid of the break statement and then execute your code.
if(name.equalsIgnoreCase(AirportName))
{
System.out.println("The name of Airport matches");
}
else
{
System.out.println("Sorry No Match Found");
}

Look closely at these two lines. There's a problem there. Step through the code in your head pretending you are the Scanner class.
line = myFile.nextLine();
String name = myFile.next();