import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonSubTypes;
import com.fasterxml.jackson.annotation.JsonTypeInfo;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.util.ArrayList;
import java.util.List;
public class Main {
public static void main(String[] args) throws JsonProcessingException {
ObjectMapper mapper = new ObjectMapper();
String json;
List<CarDiscriminator> cars = new ArrayList<>(List.of(
new Audi(3, 4, 5, new Blue()),
new Audi(3, 4, 5, new Red()),
new Toyota(3, 4, 5, null)
));
json = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(cars);
System.out.println(json);
cars = mapper.readValue(json, new TypeReference<List<CarDiscriminator>>() {
});
cars.forEach(c -> {
System.out.println(c.getClass().getSimpleName());
System.out.println(c);
});
}
static enum CarType {
AUDI, TOYOTA;
public static final String AUDI_STR = "AUDI";
public static final String TOYOTA_STR = "TOYOTA";
}
@JsonTypeInfo(
use = JsonTypeInfo.Id.NAME,
include = JsonTypeInfo.As.EXISTING_PROPERTY,
property = "carType")
@JsonSubTypes({
@JsonSubTypes.Type(value = Audi.class, name = CarType.AUDI_STR),
@JsonSubTypes.Type(value = Toyota.class, name = CarType.TOYOTA_STR)
})
@JsonInclude(JsonInclude.Include.NON_NULL)
static abstract class CarDiscriminator {
protected CarType carType;
public CarDiscriminator() {}
public CarType getCarType() {
return carType;
}
public void setCarType(CarType carType) {
this.carType = carType;
}
}
static class Audi extends CarDiscriminator {
private int attrAudi1 = 1;
private int attrAudi2 = 2;
private int attrAudi3 = 3;
private ColorDiscriminator color;
{
carType = CarType.AUDI;
}
public Audi() {}
public Audi(int attrAudi1, int attrAudi2, int attrAudi3, ColorDiscriminator color) {
this.attrAudi1 = attrAudi1;
this.attrAudi2 = attrAudi2;
this.attrAudi3 = attrAudi3;
this.color = color;
}
@Override
public String toString() {
return "Audi{" +
"attrAudi1=" + attrAudi1 +
", attrAudi2=" + attrAudi2 +
", attrAudi3=" + attrAudi3 +
", color=" + color +
", carType=" + carType +
'}';
}
public int getAttrAudi1() {
return attrAudi1;
}
public void setAttrAudi1(int attrAudi1) {
this.attrAudi1 = attrAudi1;
}
public int getAttrAudi2() {
return attrAudi2;
}
public void setAttrAudi2(int attrAudi2) {
this.attrAudi2 = attrAudi2;
}
public int getAttrAudi3() {
return attrAudi3;
}
public void setAttrAudi3(int attrAudi3) {
this.attrAudi3 = attrAudi3;
}
public ColorDiscriminator getColor() {
return color;
}
public void setColor(ColorDiscriminator color) {
this.color = color;
}
}
static class Toyota extends CarDiscriminator {
private int attrToyota1 = 1;
private int attrToyota2 = 2;
private int attrToyota3 = 3;
private ColorDiscriminator color;
{
carType = CarType.TOYOTA;
}
public Toyota() {}
public Toyota(int attrToyota1, int attrToyota2, int attrToyota3, ColorDiscriminator color) {
this.attrToyota1 = attrToyota1;
this.attrToyota2 = attrToyota2;
this.attrToyota3 = attrToyota3;
this.color = color;
}
@Override
public String toString() {
return "Toyota{" +
"attrToyota1=" + attrToyota1 +
", attrToyota2=" + attrToyota2 +
", attrToyota3=" + attrToyota3 +
", color=" + color +
", carType=" + carType +
'}';
}
public int getAttrToyota1() {
return attrToyota1;
}
public void setAttrToyota1(int attrToyota1) {
this.attrToyota1 = attrToyota1;
}
public int getAttrToyota2() {
return attrToyota2;
}
public void setAttrToyota2(int attrToyota2) {
this.attrToyota2 = attrToyota2;
}
public int getAttrToyota3() {
return attrToyota3;
}
public void setAttrToyota3(int attrToyota3) {
this.attrToyota3 = attrToyota3;
}
public ColorDiscriminator getColor() {
return color;
}
public void setColor(ColorDiscriminator color) {
this.color = color;
}
}
static enum ColorType {
BLUE, RED;
public static final String BLUE_STR = "BLUE";
public static final String RED_STR = "RED";
}
@JsonTypeInfo(
use = JsonTypeInfo.Id.NAME,
include = JsonTypeInfo.As.EXISTING_PROPERTY,
property = "colorType")
@JsonSubTypes({
@JsonSubTypes.Type(value = Blue.class, name = ColorType.BLUE_STR),
@JsonSubTypes.Type(value = Red.class, name = ColorType.RED_STR)
})
static abstract class ColorDiscriminator {
protected ColorType colorType;
public ColorDiscriminator() {}
public ColorType getColorType() {
return colorType;
}
public void setColorType(ColorType colorType) {
this.colorType = colorType;
}
}
static class Blue extends ColorDiscriminator {
private int attrBlue1 = 1;
private int attrBlue2 = 2;
private int attrBlue3 = 3;
{
colorType = ColorType.BLUE;
}
public Blue() {}
public Blue(int attrBlue1, int attrBlue2, int attrBlue3) {
this.attrBlue1 = attrBlue1;
this.attrBlue2 = attrBlue2;
this.attrBlue3 = attrBlue3;
}
@Override
public String toString() {
return "Blue{" +
"attrBlue3=" + attrBlue3 +
", attrBlue1=" + attrBlue1 +
", attrBlue2=" + attrBlue2 +
", colorType=" + colorType +
'}';
}
public int getAttrBlue1() {
return attrBlue1;
}
public void setAttrBlue1(int attrBlue1) {
this.attrBlue1 = attrBlue1;
}
public int getAttrBlue2() {
return attrBlue2;
}
public void setAttrBlue2(int attrBlue2) {
this.attrBlue2 = attrBlue2;
}
public int getAttrBlue3() {
return attrBlue3;
}
public void setAttrBlue3(int attrBlue3) {
this.attrBlue3 = attrBlue3;
}
}
static class Red extends ColorDiscriminator {
private int attrRed1 = 1;
private int attrRed2 = 2;
private int attrRed3 = 3;
{
colorType = ColorType.RED;
}
public Red() {}
public Red(int attrRed1, int attrRed2, int attrRed3) {
this.attrRed1 = attrRed1;
this.attrRed2 = attrRed2;
this.attrRed3 = attrRed3;
}
@Override
public String toString() {
return "Red{" +
"attrRed1=" + attrRed1 +
", attrRed2=" + attrRed2 +
", attrRed3=" + attrRed3 +
", colorType=" + colorType +
'}';
}
public int getAttrRed1() {
return attrRed1;
}
public void setAttrRed1(int attrRed1) {
this.attrRed1 = attrRed1;
}
public int getAttrRed2() {
return attrRed2;
}
public void setAttrRed2(int attrRed2) {
this.attrRed2 = attrRed2;
}
public int getAttrRed3() {
return attrRed3;
}
public void setAttrRed3(int attrRed3) {
this.attrRed3 = attrRed3;
}
}
} Write, Run & Share Java code online using OneCompiler's Java online compiler for free. It's one of the robust, feature-rich online compilers for Java language, running the Java LTS version 17. Getting started with the OneCompiler's Java editor is easy and fast. The editor shows sample boilerplate code when you choose language as Java and start coding.
OneCompiler's Java online editor supports stdin and users can give inputs to the programs using the STDIN textbox under the I/O tab. Using Scanner class in Java program, you can read the inputs. Following is a sample program that shows reading STDIN ( A string in this case ).
import java.util.Scanner;
class Input {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("Enter your name: ");
String inp = input.next();
System.out.println("Hello, " + inp);
}
}
OneCompiler supports Gradle for dependency management. Users can add dependencies in the build.gradle file and use them in their programs. When you add the dependencies for the first time, the first run might be a little slow as we download the dependencies, but the subsequent runs will be faster. Following sample Gradle configuration shows how to add dependencies
apply plugin:'application'
mainClassName = 'HelloWorld'
run { standardInput = System.in }
sourceSets { main { java { srcDir './' } } }
repositories {
jcenter()
}
dependencies {
// add dependencies here as below
implementation group: 'org.apache.commons', name: 'commons-lang3', version: '3.9'
}
Java is a very popular general-purpose programming language, it is class-based and object-oriented. Java was developed by James Gosling at Sun Microsystems ( later acquired by Oracle) the initial release of Java was in 1995. Java 17 is the latest long-term supported version (LTS). As of today, Java is the world's number one server programming language with a 12 million developer community, 5 million students studying worldwide and it's #1 choice for the cloud development.
short x = 999; // -32768 to 32767
int x = 99999; // -2147483648 to 2147483647
long x = 99999999999L; // -9223372036854775808 to 9223372036854775807
float x = 1.2;
double x = 99.99d;
byte x = 99; // -128 to 127
char x = 'A';
boolean x = true;
When ever you want to perform a set of operations based on a condition If-Else is used.
if(conditional-expression) {
// code
} else {
// code
}
Example:
int i = 10;
if(i % 2 == 0) {
System.out.println("i is even number");
} else {
System.out.println("i is odd number");
}
Switch is an alternative to If-Else-If ladder and to select one among many blocks of code.
switch(<conditional-expression>) {
case value1:
// code
break; // optional
case value2:
// code
break; // optional
...
default:
//code to be executed when all the above cases are not matched;
}
For loop is used to iterate a set of statements based on a condition. Usually for loop is preferred when number of iterations is known in advance.
for(Initialization; Condition; Increment/decrement){
//code
}
While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.
while(<condition>){
// code
}
Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.
do {
// code
} while (<condition>);
Class is the blueprint of an object, which is also referred as user-defined data type with variables and functions. Object is a basic unit in OOP, and is an instance of the class.
class keyword is required to create a class.
class Mobile {
public: // access specifier which specifies that accessibility of class members
string name; // string variable (attribute)
int price; // int variable (attribute)
};
Mobile m1 = new Mobile();
public class Greeting {
static void hello() {
System.out.println("Hello.. Happy learning!");
}
public static void main(String[] args) {
hello();
}
}
Collection is a group of objects which can be represented as a single unit. Collections are introduced to bring a unified common interface to all the objects.
Collection Framework was introduced since JDK 1.2 which is used to represent and manage Collections and it contains:
This framework also defines map interfaces and several classes in addition to Collections.
| Collection | Description |
|---|---|
| Set | Set is a collection of elements which can not contain duplicate values. Set is implemented in HashSets, LinkedHashSets, TreeSet etc |
| List | List is a ordered collection of elements which can have duplicates. Lists are classified into ArrayList, LinkedList, Vectors |
| Queue | FIFO approach, while instantiating Queue interface you can either choose LinkedList or PriorityQueue. |
| Deque | Deque(Double Ended Queue) is used to add or remove elements from both the ends of the Queue(both head and tail) |
| Map | Map contains key-values pairs which don't have any duplicates. Map is implemented in HashMap, TreeMap etc. |