Accessing arguments in Java - Step-by-Step Execution

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Concept Flow - Accessing arguments

Program starts

↓

Main method called with args array

↓

Access args[0

↓

Use arguments in code

↓

Program ends

The program starts and the main method receives an array of arguments. Each argument can be accessed by its index in the array and used in the program.

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Execution Sample

Java

public class Main {
  public static void main(String[] args) {
    System.out.println("First arg: " + args[0]);
    System.out.println("Second arg: " + args[1]);
  }
}

This program prints the first two command-line arguments passed to it.

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Execution Table

Step	Action	args array content	Accessed argument	Output
1	Program starts, main called	["hello", "world"]	N/A	N/A
2	Access args[0]	["hello", "world"]	"hello"	Prints: First arg: hello
3	Access args[1]	["hello", "world"]	"world"	Prints: Second arg: world
4	Program ends	["hello", "world"]	N/A	N/A

💡 All arguments accessed and printed, program ends.

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Variable Tracker

Variable	Start	After Step 2	After Step 3	Final
args	["hello", "world"]	["hello", "world"]	["hello", "world"]	["hello", "world"]
args[0]	"hello"	"hello"	"hello"	"hello"
args[1]	"world"	"world"	"world"	"world"

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Key Moments - 2 Insights

▶Why do we use args[0] and args[1] to get the first and second arguments?

▶What happens if we try to access args[2] when only two arguments are passed?

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Visual Quiz - 3 Questions

Look at the execution_table, what is the output at Step 2?

A No output

B Prints: Second arg: world

C Prints: First arg: hello

D Error

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Concept Snapshot

Access command-line arguments via the String[] args array in main.
Use args[0], args[1], etc. to get each argument.
Arguments are strings passed when running the program.
Accessing an index out of bounds causes an error.
Always check args length before accessing.

contract

Full Transcript

This visual execution shows how Java programs access command-line arguments through the main method's String array named args. The program starts and receives arguments as an array. Each argument is accessed by its index, starting at zero. The example prints the first two arguments. The execution table traces each step: program start, accessing args[0], accessing args[1], and program end. The variable tracker shows how args and its elements change or are accessed. Key moments clarify why indexing starts at zero and what happens if you access an argument that does not exist. The quiz tests understanding of output at each step and error cases. The snapshot summarizes the key points for quick reference.