package org.kodejava.util;
import java.util.*;
public class SetToArray {
public static void main(String[] args) {
// Create a java.util.Set object and add some integers into the Set.
Set<Integer> numberSet = new HashSet<>();
numberSet.add(1);
numberSet.add(2);
numberSet.add(3);
numberSet.add(5);
numberSet.add(8);
// Converting a java.util.Set into an array can be done by creating a
// java.util.List object from the Set and then convert it into an array
// by calling the toArray() method on the list object.
List<Integer> numberList = new ArrayList<>(numberSet);
Integer[] numbers = numberList.toArray(new Integer[0]);
// Display the content of numbers array.
for (int i = 0; i < numbers.length; i++) {
Integer number = numbers[i];
System.out.print(number + (i < numbers.length - 1 ? ", " : "\n"));
}
// Display the content of numbers array using the for-each loop.
for (Integer number : numbers) {
System.out.print(number + ", ");
}
}
}
Category Archives: Util Package
How do I convert Set into List?
The code below gives you an example of converting a java.util.Set into a java.util.List. It has simply done by creating a new instance of List and pass the Set as the argument of the constructor.
package org.kodejava.util;
import java.util.*;
public class SetToList {
public static void main(String[] args) {
// Create a Set and add some objects into the Set.
Set<Object> set = new HashSet<>();
set.add("A");
set.add(10L);
set.add(new Date());
// Convert the Set to a List can be done by passing the Set instance into
// the constructor of a List implementation class such as ArrayList.
List<Object> list = new ArrayList<>(set);
for (Object o : list) {
System.out.println("Object = " + o);
}
}
}
The output of the code snippet are:
Object = A
Object = 10
Object = Mon Oct 04 20:20:26 CST 2021
How do I convert Properties into Map?
package org.kodejava.util;
import java.util.Properties;
import java.util.Map;
import java.util.HashMap;
import java.util.Set;
public class PropertiesToMap {
public static void main(String[] args) {
// Create a new instance of Properties.
Properties properties = new Properties();
// Populate properties with a dummy application information
properties.setProperty("app.name", "HTML Designer");
properties.setProperty("app.version", "1.0");
properties.setProperty("app.vendor", "HTML Designer Inc");
// Create a new HashMap and pass an instance of Properties. Properties
// is an implementation of a Map which keys and values stored as in a
// String.
Map<Object, Object> map = new HashMap<>(properties);
// Get the entry set of the Map and print it out.
Set<Map.Entry<Object, Object>> propertySet = map.entrySet();
for (Map.Entry<Object, Object> entry : propertySet) {
System.out.printf("%s = %s%n", entry.getKey(), entry.getValue());
}
}
}
The output of the code snippet above:
app.vendor = HTML Designer Inc
app.name = HTML Designer
app.version = 1.0
How do I compare two dates?
In this example you’ll see the utilization of SimpleDateFormat class for comparing two dates for equality. We convert the date object into string using the DateFormat instance and then compare it using String.equals() method.
package org.kodejava.util;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
public class ComparingDate {
public static void main(String[] args) {
// Create a SimpleDateFormat instance with dd/MM/yyyy format
DateFormat df = new SimpleDateFormat("dd/MM/yyyy");
// Get the current date
Date today = new Date();
// Create an instance of calendar that represents a new year date
Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.DATE, 1);
calendar.set(Calendar.MONTH, Calendar.JANUARY);
calendar.set(Calendar.YEAR, 2021);
String newYear = df.format(calendar.getTime());
String now = df.format(today);
// Using the string equals method we can compare the date.
if (now.equals(newYear)) {
System.out.println("Happy New Year!");
} else {
System.out.println("Have a nice day!");
}
}
}
How do I convert ResourceBundle to Properties?
package org.kodejava.util;
import java.util.*;
public class ResourceBundleToProperties {
public static void main(String[] args) {
// Load resource bundle Messages_en_GB.properties from the classpath.
ResourceBundle resource = ResourceBundle.getBundle("Messages", Locale.UK);
// Call the convertResourceBundleToProperties method to convert the resource
// bundle into a Properties object.
Properties properties = convertResourceBundleToProperties(resource);
// Print the entire contents of the Properties.
Enumeration<Object> keys = properties.keys();
while (keys.hasMoreElements()) {
String key = (String) keys.nextElement();
String value = (String) properties.get(key);
System.out.println(key + " = " + value);
}
}
/**
* Convert ResourceBundle into a Properties object.
*
* @param resource a resource bundle to convert.
* @return Properties a properties version of the resource bundle.
*/
private static Properties convertResourceBundleToProperties(ResourceBundle resource) {
Properties properties = new Properties();
Enumeration<String> keys = resource.getKeys();
while (keys.hasMoreElements()) {
String key = keys.nextElement();
properties.put(key, resource.getString(key));
}
return properties;
}
}