I wanted to try to set one args argument [0] , depending on which the array will be output in direct or reverse order.
On the if (args [0] .compareto ("first") == 0) gives ArrayIndExOUTOFBOUNDSException: 0 .

What is the problem?

Public Class Main {
  Public Static Void Main (String [] Args) {
    int [] Massive = {1, 2, 3, 4, 5};
    if (args [0] .compareTo ("first") == 0) {
      For (int i = 0; I & lt; Massive.Length; I ++) {
        System.out.PrintLN (Massive [i]);
      }
    }
    ELSE If (Args [0] .compareTo ("Second") == 0) {
      For (int i = massive.length; I & gt; 0; i--) {
        System.out.PrintLN (Massive [i]);
      }
    }
    ELSE if (Args [0] == NULL || args.length == 0) {
      System.out.PrintLN ("Third");
    }
  }
}

Answer 1, Authority 100%

So, Added protection from ArrayIndexOUTOFBOUNDSException , Checks are modified (no dependence on the register of the argument), the first cycle is replaced by for-each , the second is changed so that everything would be displayed Elements of the array and did not fly the error.

Public Static Void Main (String [] Args) {
    int [] array = {1, 2, 3, 4, 5};
    if (args.length == 1 & amp; & amp; args [0] .equalsignorecase ("first")) {
      For (int anarray: array)
        System.out.printLN (Anarray);
    } ELSE if (args.length == 1 & amp; & amp; args [0] .equalsignorecase ("Second")) {
      for (int i = array.length-1; i & gt; = 0; i--)
        System.out.PrintLN (Array [i]);
    } ELSE if (args.length == 0)
      System.out.PrintLN ("Third");
  }

Run it stands through the console, the Java Main Firt / Second command
If you can set input parameters through IDE, such as in Intellij Idea, you can set about this: Run – & gt; Edit Configuration – & gt; Application In the Program Arguments field, you specify the argument (if there are several arguments, then specify it stands through the space).

Answer 2

Most likely you do not correctly convey the parameters when you start the program.
It needs to be done so

java & lt; class name with MAIN & GT; & lt; first parameter & gt; & lt; second parameter & gt;

More information about it can be read here