Using Static Blocks in Java: Configuration Class Example

Java Static Members: Exercise-5 with Solution

Static Block for Initialization
Write a Java program to create a class called Configuration with a static block that initializes a static variable 'configValue' from a configuration file (simulated with a default value). Print the value of 'configValue' in the main method.

Sample Solution:

Java Code:

Configuration.java

// Define the Configuration class
public class Configuration {
    // Declare a static variable configValue
    public static String configValue;

    // Static block to initialize configValue
    static {
        // Simulating reading from a configuration file by assigning a default value
        configValue = "Default Config Value";
        System.out.println("Static block executed: configValue initialized");
    }

    // Main method to print the value of configValue
    public static void main(String[] args) {
        // Print the value of configValue
        System.out.println("Config Value: " + configValue);
    }
}

Output:

Static block executed: configValue initialized
Config Value: Default Config Value

Explanation:

• Define the Configuration class:
• The Configuration class is defined using the class keyword.
• Declare a static variable configValue:
• The static variable configValue is declared. It will hold the configuration value.
• Static block to initialize configValue:
• A static block is used to initialize the static variable configValue.
• This block simulates reading from a configuration file by assigning a default value to configValue.
• A message is printed to indicate that the static block has been executed and configValue has been initialized.
• Main method to print the value of configValue:
• The main method is defined to test the Configuration class.
• It prints the value of configValue to the console.

Note on Java Static Members:

In the above exercise, the static members work by:

• Static Variable: The static variable configValue is associated with the class Configuration, not with any instance. It can be accessed and modified by static methods and blocks.
• Static Block: The static block is a special block of code that is executed when the class is first loaded into memory. It is used here to initialize the static variable configValue with a default value, simulating reading from a configuration file.
• Main Method: The main method prints the value of configValue, demonstrating that the static block has successfully initialized it.

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