Java Command line arguments

Question

I am trying to detect whether the  a  was entered as the first string argument

User · Answer

Use the apache commons cli if you plan on extending that past a single arg.

"The Apache Commons CLI library provides an API for parsing command line options passed to programs. It's also able to print help messages detailing the options available for a command line tool."

Commons CLI supports different types of options:

POSIX like options (ie. tar -zxvf foo.tar.gz)
GNU like long options (ie. du --human-readable --max-depth=1)
Java like properties (ie. java -Djava.awt.headless=true -Djava.net.useSystemProxies=true Foo)
Short options with value attached (ie. gcc -O2 foo.c)
long options with single hyphen (ie. ant -projecthelp)

User · Answer

Your main method has a String   argument  That contain the arguments that have been passed to your applications  it s often called args  but that s not a requirement

User · Answer

Every Java program starts with  public static void main String   args      That array of type String that main   takes as a parameter holds the command line arguments to your program   If the user runs your program as    java myProgram a   then args 0  will hold the String  a

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public class YourClass       public static void main String   args            if  args length  gt  0  amp  amp  args 0  equals  a

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Command-line arguments are passed in the first String   parameter to main    e g   public static void main  String   args         In the example above  args contains all the command-line arguments   The short  sweet answer to the question posed is   public static void main  String   args         if  args length  gt  0  amp  amp  args 0  equals   a                   first argument is  a        else              oh noes

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Try to pass value a and compare using the equals method like this   public static void main String str           boolean b   str 0  equals  a         System out println b        Follow this link to know more about Command line argument in Java

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Command line arguments are accessible via String   args parameter of main method   For first argument you can check args 0   entire code would look like  public static void main String   args        if   a  equals args 0                  do something

User · Answer

As everyone else has said    the  equals method is what you need     In the off chance you used something like   if argv 0      a     then it does not work because    compares the location of the two objects  physical equality  rather than the contents  logical equality    Since  a  from the command line and  a  in the source for your program are allocated in two different places the    cannot be used   You have to use the equals method which will check to see that both strings have the same characters   Another note     a      a  will work in many cases  because Strings are special in Java  but 99 99999999999999  of the time you want to use  equals

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Command line arguments are stored as strings in the String array String   args that is passed tomain      java  program name   arg1 arg2        Command line arguments are the inputs that accept from the command prompt while running the program  The arguments passed can be anything  Which is stored in the args   array     Display all command line information          class ArgDemo              public static void main String args                 System out println  there are   args length  command-line arguments                 for int i 0 i lt args length i                System out println  args   i      args i                  Example   java Argdemo one two   The output will be   there are 2 command line arguments  they are  arg 0  one arg 1  two

[java] Java Command line arguments

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