Add facade design pattern (#40)

Author: mperor

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/structural/facade/CPU.java

@@ -0,0 +1,16 @@
+package pl.mperor.lab.java.design.pattern.structural.facade;
+
+public class CPU {
+
+    public void freeze() {
+        System.out.println("CPU is freezing");
+    }
+
+    public void jump(long position) {
+        System.out.println("CPU jumped to " + position);
+    }
+
+    public void execute() {
+        System.out.println("CPU is executing");
+    }
+}

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/structural/facade/Computer.java

@@ -0,0 +1,6 @@
+package pl.mperor.lab.java.design.pattern.structural.facade;
+
+public interface Computer {
+
+    void start();
+}

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/structural/facade/ComputerFacade.java

@@ -0,0 +1,27 @@
+package pl.mperor.lab.java.design.pattern.structural.facade;
+
+public class ComputerFacade implements Computer {
+
+    private final static long BOOT_ADDRESS = 0x0;
+    private final static long BOOT_SECTOR = 0xF;
+    private final static int SECTOR_SIZE = 16;
+
+    private final CPU processor;
+    private final Memory ram;
+    private final HardDrive hd;
+
+    public ComputerFacade() {
+        this.processor = new CPU();
+        this.ram = new Memory();
+        this.hd = new HardDrive();
+    }
+
+    @Override
+    public void start() {
+        processor.freeze();
+        byte[] data = hd.read(BOOT_SECTOR, SECTOR_SIZE);
+        ram.load(BOOT_ADDRESS, data);
+        processor.jump(BOOT_ADDRESS);
+        processor.execute();
+    }
+}

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/structural/facade/HardDrive.java

@@ -0,0 +1,9 @@
+package pl.mperor.lab.java.design.pattern.structural.facade;
+
+public class HardDrive {
+
+    public byte[] read(long lba, int size) {
+        System.out.println(size + " bits is reading from " + lba);
+        return new byte[size];
+    }
+}

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/structural/facade/Memory.java

@@ -0,0 +1,8 @@
+package pl.mperor.lab.java.design.pattern.structural.facade;
+
+public class Memory {
+
+    public void load(long position, byte[] data) {
+        System.out.println("Data are loading");
+    }
+}

DesignPatterns/src/test/java/pl/mperor/lab/java/design/pattern/structural/facade/ComputerFacadeTest.java

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+package pl.mperor.lab.java.design.pattern.structural.facade;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+import pl.mperor.lab.common.TestUtils;
+
+public class ComputerFacadeTest {
+
+    @Test
+    public void shouldAllowToRunComputerInVerySimpleWayHidingItsComplexity() {
+        var out = TestUtils.setTempSystemOut();
+        Computer pc = new ComputerFacade();
+        pc.start();
+        Assertions.assertNotNull(pc);
+        Assertions.assertTrue(out.all().contains("CPU is executing"));
+        TestUtils.resetSystemOut();
+    }
+
+}