Java – Create Immutable Class Example

// declare class as final
final class Immutable {

    // declare all variables as final
    private final int val1;
    private final String val2;

    // provide constructor to set the values
    public Immutable(int a, String s) {
        val1 = a;
	val2 = s;
    }

    // provide getters only
    public int getVal1() {
        return val1;
    }

    public String getVal2() {
        return val2;
    }
}
public class ImmutableClassDemo {
    public static void main(String[] args) {
        Immutable obj = new Immutable(10, "Immutable Class Example");
	System.out.println(obj.getVal1());
	System.out.println(obj.getVal2());
   }
}

Java – Detect Operating System

public class OSValidator {

	public static void main(String[] args) {
		if (isWindows()) {
			System.out.println("This is Windows");
		} else if (isMac()) {
			System.out.println("This is Mac");
		} else if (isUnix()) {
			System.out.println("This is Unix or Linux");
		} else if (isSolaris()) {
			System.out.println("This is Solaris");
		} else {
			System.out.println("Your OS is not support!!");
		}
	}

	public static boolean isWindows() {

		String os = System.getProperty("os.name").toLowerCase();
		// windows
		return (os.indexOf("win") >= 0);

	}

	public static boolean isMac() {

		String os = System.getProperty("os.name").toLowerCase();
		// Mac
		return (os.indexOf("mac") >= 0);

	}

	public static boolean isUnix() {

		String os = System.getProperty("os.name").toLowerCase();
		// linux or unix
		return (os.indexOf("nix") >= 0 || os.indexOf("nux") >= 0);

	}

	public static boolean isSolaris() {

		String os = System.getProperty("os.name").toLowerCase();
		// Solaris
		return (os.indexOf("sunos") >= 0);

	}

}

Java – Calculate Execution Time

import java.util.Date;

public class TimeMillisecond {
  public static void main(String[] argv) {

      long lStartTime = new Date().getTime(); //start time

      String sArray1[] = createArray(); //method execute

      long lEndTime = new Date().getTime(); //end time

      long difference = lEndTime - lStartTime; //check different

      System.out.println("Elapsed milliseconds: " + difference);

  }

  static String [] createArray(){

	  String sArray[] = new String [100000];

	  for(int i=0; i<100000; i++)
		  sArray[i] = "Array " + i;

	  return sArray;
  }
}

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