moving code from java-core to java-core-lang (#6084)

core-java-lang/src/main/java/com/baeldung/interfaces/Box.java

@@ -0,0 +1,5 @@
+package com.baeldung.interfaces;
+
+public interface Box extends HasColor {
+    int getHeight();
+}

core-java-lang/src/main/java/com/baeldung/interfaces/Employee.java

@@ -0,0 +1,14 @@
+package com.baeldung.interfaces;
+
+public class Employee {
+
+    private double salary;
+
+    public double getSalary() {
+        return salary;
+    }
+
+    public void setSalary(double salary) {
+        this.salary = salary;
+    }
+}

core-java-lang/src/main/java/com/baeldung/interfaces/EmployeeSalaryComparator.java

@@ -0,0 +1,17 @@
+package com.baeldung.interfaces;
+
+import java.util.Comparator;
+
+public class EmployeeSalaryComparator implements Comparator<Employee> {
+
+    @Override
+    public int compare(Employee employeeA, Employee employeeB) {
+        if (employeeA.getSalary() < employeeB.getSalary()) {
+            return -1;
+        } else if (employeeA.getSalary() > employeeB.getSalary()) {
+            return 1;
+        } else {
+            return 0;
+        }
+    }
+}

core-java-lang/src/main/java/com/baeldung/interfaces/HasColor.java

@@ -0,0 +1,4 @@
+package com.baeldung.interfaces;
+
+public interface HasColor {
+}

core-java-lang/src/main/java/com/baeldung/interfaces/multiinheritance/Car.java

@@ -0,0 +1,14 @@
+package com.baeldung.interfaces.multiinheritance;
+
+public class Car implements Fly,Transform {
+
+    @Override
+    public void fly() {
+        System.out.println("I can Fly!!");
+    }
+
+    @Override
+    public void transform() {
+        System.out.println("I can Transform!!");
+    }
+}

core-java-lang/src/main/java/com/baeldung/interfaces/multiinheritance/Fly.java

@@ -0,0 +1,6 @@
+package com.baeldung.interfaces.multiinheritance;
+
+public interface Fly {
+
+    void fly();
+}

core-java-lang/src/main/java/com/baeldung/interfaces/multiinheritance/Transform.java

@@ -0,0 +1,10 @@
+package com.baeldung.interfaces.multiinheritance;
+
+public interface Transform {
+
+    void transform();
+
+    default void printSpecs(){
+        System.out.println("Transform Specification");
+    }
+}

core-java-lang/src/main/java/com/baeldung/interfaces/multiinheritance/Vehicle.java

@@ -0,0 +1,4 @@
+package com.baeldung.interfaces.multiinheritance;
+
+public abstract class Vehicle implements Transform {
+}

core-java-lang/src/main/java/com/baeldung/interfaces/polymorphysim/Circle.java

@@ -0,0 +1,9 @@
+package com.baeldung.interfaces.polymorphysim;
+
+public class Circle implements Shape {
+
+    @Override
+    public String name() {
+        return "Circle";
+    }
+}

core-java-lang/src/main/java/com/baeldung/interfaces/polymorphysim/MainTestClass.java

@@ -0,0 +1,20 @@
+package com.baeldung.interfaces.polymorphysim;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class MainTestClass {
+
+    public static void main(String[] args) {
+        List<Shape> shapes = new ArrayList<>();
+        Shape circleShape = new Circle();
+        Shape squareShape = new Square();
+
+        shapes.add(circleShape);
+        shapes.add(squareShape);
+
+        for (Shape shape : shapes) {
+            System.out.println(shape.name());
+        }
+    }
+}

core-java-lang/src/main/java/com/baeldung/interfaces/polymorphysim/Shape.java

@@ -0,0 +1,6 @@
+package com.baeldung.interfaces.polymorphysim;
+
+public interface Shape {
+
+    String name();
+}

core-java-lang/src/main/java/com/baeldung/interfaces/polymorphysim/Square.java

@@ -0,0 +1,9 @@
+package com.baeldung.interfaces.polymorphysim;
+
+public class Square implements Shape {
+
+    @Override
+    public String name() {
+        return "Square";
+    }
+}