Merge pull request eugenp#338 from giuseppebueti/master

Double column operator

core-java-8/src/main/java/com/baeldung/doublecolumn/Computer.java

@@ -0,0 +1,75 @@
+package com.baeldung.doublecolumn;
+
+
+public class Computer {
+
+    private Integer age;
+    private String color;
+    private Integer healty;
+
+    public Computer(int age, String color) {
+        this.age = age;
+        this.color = color;
+    }
+
+    public Computer(Integer age, String color, Integer healty) {
+        this.age = age;
+        this.color = color;
+        this.healty = healty;
+    }
+
+    public Computer() {
+    }
+
+    public Integer getAge() {
+        return age;
+    }
+
+    public void setAge(Integer age) {
+        this.age = age;
+    }
+
+    public String getColor() {
+        return color;
+    }
+
+    public void setColor(String color) {
+        this.color = color;
+    }
+
+    public Integer getHealty() {
+        return healty;
+    }
+
+    public void setHealty(Integer healty) {
+        this.healty = healty;
+    }
+
+    @Override
+    public String toString() {
+        return "Computer{" +
+                "age=" + age +
+                ", color='" + color + '\'' +
+                ", healty=" + healty +
+                '}';
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+
+        Computer computer = (Computer) o;
+
+        if (age != null ? !age.equals(computer.age) : computer.age != null) return false;
+        return color != null ? color.equals(computer.color) : computer.color == null;
+
+    }
+
+    @Override
+    public int hashCode() {
+        int result = age != null ? age.hashCode() : 0;
+        result = 31 * result + (color != null ? color.hashCode() : 0);
+        return result;
+    }
+}

core-java-8/src/main/java/com/baeldung/doublecolumn/ComputerUtils.java

@@ -0,0 +1,30 @@
+package com.baeldung.doublecolumn;
+
+import com.baeldung.doublecolumn.function.ComputerPredicate;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class ComputerUtils {
+
+
+    public static final ComputerPredicate after2010Predicate = (c ) -> ( c.getAge() > 2010 );
+    public static final ComputerPredicate blackPredicate = ( c ) -> "black".equals(c.getColor());
+
+    public static List<Computer> filter(List<Computer> inventory, ComputerPredicate p){
+
+        List<Computer> result = new ArrayList<>();
+        inventory.stream().filter(p::filter).forEach(result::add);
+
+        return result;
+    }
+
+
+    public static void repair (Computer computer){
+        if(computer.getHealty()<50){
+            computer.setHealty(100);
+        }
+    }
+
+
+}

core-java-8/src/main/java/com/baeldung/doublecolumn/function/ComputerPredicate.java

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+package com.baeldung.doublecolumn.function;
+
+import com.baeldung.doublecolumn.Computer;
+
+
+@FunctionalInterface
+public interface ComputerPredicate {
+
+    boolean filter(Computer c);
+
+}

core-java-8/src/main/java/com/baeldung/doublecolumn/function/TriFunction.java

@@ -0,0 +1,16 @@
+package com.baeldung.doublecolumn.function;
+
+import java.util.Objects;
+import java.util.function.Function;
+
+@FunctionalInterface
+public interface TriFunction<A,B,C,R> {
+
+    R apply(A a, B b, C c);
+
+    default <V> TriFunction<A, B, C, V> andThen(
+            Function<? super R, ? extends V> after) {
+        Objects.requireNonNull(after);
+        return (A a, B b, C c) -> after.apply(apply(a, b, c));
+    }
+}

core-java-8/src/test/java/com/baeldung/doublecolumn/TestComputerUtils.java

@@ -0,0 +1,70 @@
+package com.baeldung.doublecolumn;
+
+import com.baeldung.doublecolumn.function.TriFunction;
+import org.junit.After;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.*;
+import java.util.function.BiFunction;
+
+import static com.baeldung.doublecolumn.ComputerUtils.*;
+
+public class TestComputerUtils {
+
+
+    @Before
+    public void setup (){
+    }
+
+    @After
+    public void tearDown(){
+    }
+
+    @Test
+    public void testFilter(){
+
+        Computer c1=new Computer(2015,"white");
+        Computer c2=new Computer(2009,"black");
+        Computer c3=new Computer(2014,"black");
+
+        BiFunction<Integer,String,Computer> c4Function=Computer::new;
+        Computer c4=c4Function.apply(2013,"white");
+        BiFunction<Integer,String,Computer> c5Function=Computer::new;
+        Computer c5=c5Function.apply(2010,"black");
+        BiFunction<Integer,String,Computer> c6Function=Computer::new;
+        Computer c6=c6Function.apply(2008,"black");
+
+        List<Computer> inventory = Arrays.asList(c1,c2,c3,c4,c5,c6);
+
+        List<Computer> blackComputer = filter(inventory, blackPredicate);
+        Assert.assertEquals("The black Computers are: ",blackComputer.size(),4);
+
+        List<Computer> after2010Computer = filter(inventory, after2010Predicate);
+        Assert.assertEquals("The Computer bought after 2010 are: ",after2010Computer.size(),3);
+
+        List<Computer> before2011Computer = filter(inventory, c -> c.getAge() < 2011);
+        Assert.assertEquals("The Computer bought before 2011 are: ",before2011Computer.size(),3);
+
+        inventory.sort(Comparator.comparing(Computer::getAge));
+
+        Assert.assertEquals("Oldest Computer in inventory", c6,inventory.get(0) );
+
+    }
+
+    @Test
+    public void testRepair() {
+
+        Computer c1 = new Computer(2015, "white", 35);
+        Computer c2 = new Computer(2009, "black", 65);
+        TriFunction<Integer, String, Integer, Computer> c6Function = Computer::new;
+        Computer c3 = c6Function.apply(2008, "black", 90);
+
+        List<Computer> inventory = Arrays.asList(c1, c2, c3);
+        inventory.forEach(ComputerUtils::repair);
+
+        Assert.assertEquals("Computer repaired", new Integer(100), c1.getHealty());
+    }
+
+}