Deep & Shallow Copy

core-java-modules/core-java-lang-5/src/main/java/com/baeldung/shallowdeep/Car.java

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+package com.baeldung.shallowdeep;
+
+public class Car {
+
+    private int modelNumber;
+	private String modelName;
+	private Engine engine;
+	public Car(int modelNumber, Engine engine, String modelName) {
+		super();
+		this.modelNumber = modelNumber;
+		this.engine = engine;
+		this.modelName = modelName;
+	}
+	public Car(Car car) {
+		this.modelNumber=car.modelNumber;
+		this.modelName=car.modelName;
+		this.engine=new Engine(car.getEngine());
+	}
+	
+	public int getModelNumber() {
+		return modelNumber;
+	}
+	public void setModelNumber(int modelNumber) {
+		this.modelNumber = modelNumber;
+	}
+	public Engine getEngine() {
+		return engine;
+	}
+	public void setEngine(Engine engine) {
+		this.engine = engine;
+	}
+	public String getModelName() {
+		return modelName;
+	}
+	public void setModelName(String modelName) {
+		this.modelName = modelName;
+	}
+}

core-java-modules/core-java-lang-5/src/main/java/com/baeldung/shallowdeep/Engine.java

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+package com.baeldung.shallowdeep;
+
+public class Engine {
+	private String type;
+	private double horsePower;
+	
+	public String getType() {
+		return type;
+	}
+	public void setType(String type) {
+		this.type = type;
+	}
+	public double getHorsePower() {
+		return horsePower;
+	}
+	public void setHorsePower(double horsePower) {
+		this.horsePower = horsePower;
+	}
+	public Engine(String type, double horsePower) {
+		super();
+		this.type = type;
+		this.horsePower = horsePower;
+	}
+	public Engine(Engine engine) {
+		this.type=engine.type;
+		this.horsePower=engine.horsePower;
+	}
+}

core-java-modules/core-java-lang-5/src/test/java/com/baeldung/shallowdeep/DeepShallowCopyUnitTest.java

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+package com.baeldung.shallowdeep;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class DeepShallowCopyUnitTest {
+
+	@Test
+	public void givenImmutable_whenShallowCopied_thenObjectsShouldBeDifferent() {
+
+		Engine engine = new Engine("Four-stroked", 130);
+		Car car = new Car(123, engine, "Toyota Corolla");
+
+		Car shallowCopiedCar = new Car(car.getModelNumber(), car.getEngine(), car.getModelName());
+		car.setModelName("Modified-Toyota Corolla");
+		Assert.assertNotEquals(car.getModelName(), shallowCopiedCar.getModelName());
+
+	}
+
+	@Test
+	public void whenShallowCopied_thenObjectsShouldBeDifferent() {
+
+		Engine engine = new Engine("Four-stroked", 130);
+		Car car = new Car(123, engine, "Toyota Corolla");
+		Car shallowCopiedCar = new Car(car.getModelNumber(), car.getEngine(), car.getModelName());
+		engine.setType("Two-Stroked");
+		Assert.assertSame(car.getEngine().getType(), shallowCopiedCar.getEngine().getType());
+
+	}
+
+	@Test
+	public void whenShallowCopied_thenComponentObjectsShouldBeSame() {
+
+		Engine engine = new Engine("Four-stroked", 130);
+		Car car = new Car(123, engine, "Toyota Corolla");
+
+		Car shallowCopiedCar = new Car(car.getModelNumber(), car.getEngine(), car.getModelName());
+		car.getEngine().setType("Two-stroked");
+		Assert.assertEquals(car.getEngine().getType(), shallowCopiedCar.getEngine().getType());
+
+	}
+
+	@Test
+	public void givenCopyConstructor_whenDeepCopied_ObjectsShouldBeDifferent() {
+		Engine engine = new Engine("Four-stroked", 130);
+		Car car = new Car(123, engine, "Toyota Corolla");
+		Car deepCopiedCar = new Car(car);
+		car.getEngine().setType("Two-stroked");
+		Assert.assertNotEquals(car.getEngine().getType(), deepCopiedCar.getEngine().getType());
+	}
+
+}