I've been trying for 1 week to run a simple java program using third party jar, but I keep getting error. Just now I try this program as below
import org.apache.commons.lang3.*;
public class HelloWorld{
public static void main(String[] args){
String x = "abcd";
System.out.println(StringUtils.capitalize(x));
}
}
and when I try to compile and run, command prompt return error as below
c:\training\java\exercise>javac -cp ".;./org/apache/commons/lang3/commons-lang3-3.9.jar" HelloWorld.java
HelloWorld.java:5: error: cannot find symbol
System.out.println(StringUtils.capitalize(x));
I take this example from this sites as for reference https://www.programcreek.com/2014/01/compile-and-run-java-in-command-line-with-external-jars/
can anyone help me how to solve this? Thanks in advance
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There is an article about just that available here
I assume you're on Windows as the working folder has disk C: so it should be Windows.
Bottom line it looks like you're mixing the notions of folder and jar.
Make sure that the folder C:\training\java\exercise contains both HelloWorld.java and commons-lang3-3.9.jar
Also make sure you're in the C:\training\java\exercise folder
Then compile like this:
javac -cp ".;./commons-lang3-3.9.jar" HelloWorld.java
Now this should create HelloWorld.class file
Now Run the java process:
java -cp ".;./commons-lang3-3.9.jar" HelloWorld
Related
I am trying to learn Java and I've made my first program and compiled it into a class file (the file is called aye.java and when compiled I have aye.class, I think the compilation worked). However when I use the java command in the folder where the class is located it just returns below error -
Could not find or load main class aye.class.
I have tried including the package name (com.java24hours) but it still doesn't work.. please help!
Commands I have tried:
java aye.class
java com.java24hours.aye.class
java aye
java com.java24hours.aye
program code:
package com.java24hours;
class aye {
public static void main(String[] args) {
//java code yeet
String aye = "Hello World!";
System.out.println(aye);
}
}
(I am running Linux on a Chromebook and have installed Java via the ppa:webupd8team/java)
Thanks.
I suppose you wanna put binaries to ./bin folder.
Compile aye.java:
javac -d ./bin aye.java
Then cd to ./bin directory and run the program:
cd bin
java com.java24hours.aye
well im stupid
since im new to java, i didn't know anything about packages and such. turns out all i had to do was put the class file in a folder named "ya" (that's the name of the package - i updated the program) and run the command
java -cp /home/ramsey/Documents/ya aye
(-cp stands for classpath, and you use it when you want to specify where you class is located MAKE SURE TO PUT IT IN A FOLDER NAMED AFTER YOUR PACKAGE!!!)
the wiki page is helpful: https://en.wikipedia.org/wiki/Classpath_(Java)
its under the section setting the path to execute java programs
thanks for the help everyone!
Hello stackoverflow community!
I am in the beginning of my journey of becoming a programmer and currently in the process of learning Java. I have strictly been using Eclipse to compile my programs. However, when I try to run the program through the command line I get:
"Error: Could not find or load main class FirstProg."
I've read through some other discussions on the forum and experimented with different methods, but I cannot get it to execute the program.
The path to my program (FirstProg.java) is as follows: C:\Users\smj7v\workspace\LearningJava\src\com\smj\programmingByDoing
When I enter "javac FirstProg.java" in the CMD it compiles the program and I can see the FirstProg.class generated in the path folder, but when I try to execute, "java FirstProg," it throws the error.
I tried doing things like "java com.smj.programmingByDoing.FirstProg" along with other variations but so far nothing has worked. Obviously I am doing something wrong. Please help!
public class FirstProg {
public static void main(String[] args) {
System.out.println("Mr. Mitchell is cool.");
}
}
The program runs fine in Eclipse btw.
here's a sample way of doing
create following class MyTest.java under c:\com\test folder
package com.test;
public class MyTest
{
public static void main(String[] args)
{
System.out.println("test fle");
}
}
now when you are compiling make sure that you use option -d
run following
cd \com\test
javac -d . mytest.java
next from same folder (com\test),
java com.test.MyTest
Step 1: Write Java Program.
Step 2: Compile java file to class file and generate byte code.
Step 3: Byte code translate to machine code and run on JVM.
Steps to write, compile and run java program using command prompt.
(i). Save the program. After using a text editor, such as NotePad, to create your Java program, save the program with a .java extension.
(ii). Open Command Prompt.
(iii). Navigate to the correct folder.
(iv). Set path.
(v). Compile the program.
Example:javac JavaClassName.java
(vi). Run the program.
Example:java JavaClassName
Visit the good blog to read all steps with example and images:
https://javatutorialdetails.blogspot.in/2017/10/how-java-program-work-step-by-step-in.html
Run your class after setting classpath:
set classpath=%classpath%;.;
java com.smj.programmingByDoing.FirstProg
C:\Users\smj7v\workspace\LearningJava\src> javac com\smj\programmingByDoing\FirstProg.java
C:\Users\smj7v\workspace\LearningJava\src> set classpath=%classpath%;.;
C:\Users\smj7v\workspace\LearningJava\src> java com.smj.programmingByDoing.FirstProg
The principal class XXXX has not been found
The code constructs perfectly but when I try to execute it I get the same error again.
I type the following "Hello world" code:
public class Hello {
public static void main(String[] args) {
System.out.println("Hola mundo");
}
}
I get the same error.
It must be a problem of my program ,I use GEANY because my teacher told me that I can't use netbean or similar.
How do you compile and execute your code? Is it some IDE (Eclipse) or just command line?
IDE should take care about this issue. In command line you have to include all classes into the classpath. Sometime it is confusing because when you compile your code mutually is in classpath but you have to mention it litreally to run.
Here is example
javac Hello.java
compiles Hello.java source to the Hello.class code to the current location. Literally ./Hello.class
To run you should mention this location
java -classpath . Hello
without -classpath . java doesn't know where your class is.
I have problem running a basic helloworld application in Java form my command-line in widnows 7. I can run it in Java.
Here is my code(in NetBeans):
package helloworld;
public class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello World!");
}
}
I have set C:\Program Files\Java\jdk1.8.0_20\bin; on my PATH variable in the Windows Environment.
When running :
javac HelloWorld.java
the HelloWorld.class is built successfully.
However in the next step when I run:
java HelloWorld
I get he following error:
Error: Could not find or load main class HelloWorld
Under my program source root directory I can see these two file:
. HelloWorld.class
. HelloWorld.java
What am I missing please?
You should specify fully qualified class name. That is, you need to run it like that: java helloworld.HelloWorld.
what you need to do is as you have
package helloworld;
and you are trying to execute it from the commandline
do the following steps
First open the terminal or cmd and browse to the folder helloworld.
Example if your helloworld folder in in f:/helloworld open the terminal and browse upto f:/(don't go inside helloworld)
then compile the class as javac helloworld/HelloWorld.java
and try executing the class as java helloworld.HelloWorld
the class name was not fully qualified, try java helloworld.HelloWorld
the .classfile should not be in the directory the java command is run from.
you forgot the helloworld package. So you have to enter java helloworld.HelloWorld to make it work. Next time please use a different package name than the java file, so there is no confusion. :)
I am very new to linux environment.
I am trying to run an simple hello world java class in linux environment.
Hello .java
package com.util;
public class Hello {
/**
* #param args
*/
public static void main(String[] args) {
System.out.println("hi");
}
}
I have compiled java class in windows environment and uploaded the .class file to linux system into /home/scripts path.
my command is as follows,
java -cp /home/scripts com.util.Hello
when i am executing this command from this same /home/scripts where Hello.class is there i am getting,
Error: Could not find or load main class com.util.Hello and not able to proceed further.
can some one help me in this issue?
navigate to /home/scripts using terminal
javac com/util/Hello.java
then
cd /home/scripts
java -cp . com.util.Hello
Or,
java -cp "/home/scripts" com.util.Hello
At first you must generate your .class file :
javac ./hello.java
This command has generated hello.class file
And after you can run your class file ! :)
java hello
We first know javac command work well.
I also met this error,and i have resolved this.Let me share this.
First we need to find the parent path of your package in your java codes.
Then cd to that path using java package + fileName should work well at that moment.
I had the exact same issue on windows, and I solved it by adding path "." to both CLASSPATH and PATH, maybe you can try this on Linux as well.
Your .class file should not reside in /home/scripts/, but in /home/scripts/com/util/. Take a look at this document that explains the relation between classpath, packages and directories.
Before Specifying the path,ensure you follow these three things meticulously,
1. Close the command prompt window, before specifying the path.
2. When adding path, add bin and semi- colon at the end and
3. If JAVAC command has worked properly, try java -cp class name.
if you want to run program in current working directory where your class reside.
java gives three options.
first option
java -cp Tester
Second option for current working directory
java -cp . Tester
Third option export CLASSPATH variable
export CLASSPATH=$CLASSPATH:. (this is the best one if your directory changes) or
export CLASSPATH=$PWD
or
export CLASSPATH=
after that you must sorce the bashrc or bashprofile.