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Programming Articles
Page 1516 of 2547
Java Program to create String to super class type mapping
Here, we have a superclass Vehicle and within that some subclasses −class Vehicle { } class Motorcycle extends Vehicle { } class Bus extends Vehicle { } class Car extends Vehicle { }Now, we will create some strings for mapping with super class type −Mapmap = new HashMap(); map.put("motorcycle", new Motorcycle()); map.put("bus", new Bus()); map.put("car", new Car());Exampleimport java.util.HashMap; import java.util.Map; class Vehicle { } class Motorcycle extends Vehicle { } class Bus extends Vehicle { } class Car extends Vehicle { } public class Demo { public static void main(String... args) { Mapmap = new HashMap(); ...
Read MoreExtract values from HashMap in Java
To extract values from HashMap, let us first create a HashMap with keys and values −HashMapm = new HashMap();Now, add some elements to the HashMap −m.put(10, 20); m.put(30, 40); m.put(50, 60); m.put(70, 80); m.put(90, 100); m.put(110, 120); m.put(130, 140); m.put(150, 160);Now, extract the values from the HashMap −for (Integer i: m.keySet()) { System.out.println(m.get(i)); }Exampleimport java.util.HashMap; public class Demo { public static void main(String args[]) { HashMapm = new HashMap(); m.put(10, 20); m.put(30, 40); m.put(50, 60); m.put(70, 80); m.put(90, 100); ...
Read MoreIs it possible to assign a reference to "this" in java?
The "this" keyword in Java is used as a reference to the current object, within an instance method or a constructor. Using it, you can refer the members of a class such as constructors, variables, and methods.Assigning reference to "this"According to the definition "this" is a keyword which acts as a reference to the current object (the object from whose constructor/method you are using it), its value id is fixed. Therefore, you cannot assign a new reference value to it. Moreover, it is just a keyword, not a variable.Still, if you try to it assign a reference value to "this" it ...
Read MoreHow to keep the insertion order with Java LinkedHashMap?
To keep the insertion order with LinkedHashMap, use Iterator. Let us first create a HashMap and add elements to it −LinkedHashMaplHashMap = new LinkedHashMap(); lHashMap.put("1", "A"); lHashMap.put("2", "B"); lHashMap.put("3", "C"); lHashMap.put("4", "D"); lHashMap.put("5", "E"); lHashMap.put("6", "F"); lHashMap.put("7", "G"); lHashMap.put("8", "H"); lHashMap.put("9", "I");Now, get the values with the values() method. Iterate through the elements and display them −Collection collection = lHashMap.values(); Iterator i = collection.iterator(); while (i.hasNext()) { System.out.println(i.next()); }Exampleimport java.util.Collection; import java.util.Iterator; import java.util.LinkedHashMap; public class Demo { public static void main(String[] args) { LinkedHashMaplHashMap = new LinkedHashMap(); lHashMap.put("1", "A"); ...
Read MoreWhat happens if we call "super()" in a constructor without extending any class, in java?
A super keyword is a reference of the superclass object in Java. Using this, you can invoke the instance methods constructors and, variables, of a superclass.Calling the constructor of a superclassYou can call the constructor of a superclass from the subclass’s constructor.ExampleConsider the following example, it has two classes SuperClass class and SubClass where the SubClass extends the SuperClass. The superclass has a parameterized constructor, we are invoking it from the subclass using the "super" keyword.class SuperClass{ SuperClass(int data){ System.out.println("Superclass's constructor: "+data); } } public class SubClass extends SuperClass{ SubClass(int data) { super(data); ...
Read MoreProvider toString() method in Java
The name and the version number of the provider in string form can be obtained using the method toString() in the class java.security.Provider. This method requires no parameters and it returns the name as well as the version number of the provider in string form.A program that demonstrates this is given as follows −Exampleimport java.security.*; import java.util.*; public class Demo { public static void main(String[] argv) { try { KeyPairGenerator kpGenerator = KeyPairGenerator.getInstance("DSA"); Provider p = kpGenerator.getProvider(); System.out.println("The name and version number of the ...
Read MoreProgram to convert Primitive Array to Stream in Java
To convert Primitive Array to Stream, you need to use the of() method.Let’s say the following is our Primitive Array:int[] myArr = new int[] { 20, 50, 70, 90, 100, 120, 150 };Now, use the of() method to convert the primitive array to stream:IntStream stream = IntStream.of(myArr);The following is an example to convert primitive array to stream in Java:Exampleimport java.util.stream.IntStream; import java.util.*; public class Main { public static void main(String[] args) { int[] myArr = new int[] { 20, 50, 70, 90, 100, 120, 150 }; System.out.println("The Primitive Array = "+Arrays.toString(myArr)); ...
Read MoreJava Program to loop through Map by Map.Entry
Create a Map and insert elements to in the form of key and value −HashMap map = new HashMap (); map.put("1", "A"); map.put("2", "B"); map.put("3", "C"); map.put("4", "D"); map.put("5", "E"); map.put("6", "F"); map.put("7", "G"); map.put("8", "H"); map.put("9", "I");Now, loop through Map by Map.Entry. Here, we have displayed the key and value separately −Sets = map.entrySet(); Iteratori = s.iterator(); while (i.hasNext()) { Map.Entrye = (Map.Entry) i.next(); String key = (String) e.getKey(); String value = (String) e.getValue(); System.out.println("Key = "+key + " => Value = "+ value); }Exampleimport java.util.HashMap; import java.util.Iterator; import java.util.LinkedHashMap; import java.util.Map; import ...
Read MoreJava Program to read map by Map.Entry
To read the Map, first use getProperties() ad then iterator to iterate through the entire list of Map −Properties prop = System.getProperties(); Iterator i = prop.entrySet().iterator();Now, loop through Map.Entry and get the key-value pair for the Map −while (i.hasNext()) { Map.Entry entry = (Map.Entry) i.next(); System.out.println(entry.getKey() + " => " + entry.getValue()); }Exampleimport java.util.Iterator; import java.util.Map; import java.util.Properties; public class Demo { public static void main(String[] a) { Properties prop = System.getProperties(); Iterator i = prop.entrySet().iterator(); while (i.hasNext()) { Map.Entry entry = (Map.Entry) i.next(); ...
Read MoreCan we call Superclass's static method from subclass in Java?
A static method is the one which you can call without instantiating the class. If you want to call a static method of the superclass, you can call it directly using the class name.Examplepublic class Sample{ public static void display(){ System.out.println("This is the static method........"); } public static void main(String args[]){ Sample.display(); } }OutputThis is the static method........It also works, if you call a static method using an instance. But, it is not recommended.public class Sample{ public static void display(){ System.out.println("This is the static method........"); ...
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