Implemented restriction operators.

Author: brettryan

src/main/java/com/drunkendev/lambdas/RestrictionOperators.java

@@ -0,0 +1,130 @@
+/*
+ * RestrictionOperators.java    Feb 2 2014, 03:01
+ *
+ * Copyright 2014 Drunken Dev.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.drunkendev.lambdas;
+
+import com.drunkendev.lambdas.domain.DomainService;
+import com.drunkendev.lambdas.helper.IndexHolder;
+import java.math.BigDecimal;
+import java.time.format.DateTimeFormatter;
+import java.util.Arrays;
+import java.util.List;
+
+
+/**
+ *
+ * @author  Brett Ryan
+ */
+public class RestrictionOperators {
+
+    private final DomainService ds;
+
+    /**
+     * Creates a new {@code RestrictionOperators} instance.
+     */
+    public RestrictionOperators() {
+        this.ds = new DomainService();
+    }
+
+    public static void main(String[] args) {
+        RestrictionOperators ro = new RestrictionOperators();
+        ro.lambda1();
+        ro.lambda2();
+        ro.lambda3();
+        ro.lambda4();
+        ro.lambda5();
+    }
+
+    /**
+     * This sample uses a filter to find all elements of a list with a value
+     * less than 5.
+     */
+    public void lambda1() {
+        System.out.println("\nNumbers < 5:");
+        List<Integer> numbers = Arrays.asList(5, 4, 1, 3, 9, 8, 6, 7, 2, 0);
+        numbers.stream()
+                .filter(n -> n < 5)
+                .forEach(System.out::println);
+    }
+
+    /**
+     * This sample uses a filter to find all products that are out of stock.
+     */
+    public void lambda2() {
+        System.out.println("\nSold out products:");
+        ds.getProductList().stream()
+                .filter(x -> x.getUnitsInStock() == 0)
+                .forEach(x -> {
+                    System.out.println(String.format("%s is sold out!",
+                                                     x.getProductName()));
+                });
+    }
+
+    /**
+     * This sample uses a filter to find all products that are in stock and cost
+     * more than 3.00 per unit.
+     */
+    public void lambda3() {
+        System.out.println("\nIn-stock products that cost more than 3.00:");
+        ds.getProductList().stream()
+                .filter(x -> x.getUnitsInStock() > 0)
+                .filter(x -> x.getUnitPrice().compareTo(BigDecimal.valueOf(3)) > 0)
+                .forEach(x -> {
+                    System.out.println(String.format(
+                                    "%s is in stock and costs more than 3.00.",
+                                    x.getProductName()));
+                });
+    }
+
+    /**
+     * This sample uses a filter to find all customers in Washington and then it
+     * uses a forEach to iterate over the orders collection that belongs to each
+     * customer.
+     *
+     */
+    public void lambda4() {
+        System.out.println("\nCustomers from Washington and their orders:");
+        ds.getCustomerList().stream()
+                .filter(c -> "WA".equalsIgnoreCase(c.getRegion()))
+                .forEach(c -> {
+                    System.out.println(String.format("Customer %s: %s", c.getCustomerId(), c.getCompanyName()));
+                    c.getOrders().getOrders().stream().forEach(o -> {
+                        System.out.println(String.format(
+                                        "  Order %d: %s",
+                                        o.getOrderId(), o.getOrderDate().format(DateTimeFormatter.ISO_DATE)));
+
+                    });
+                });
+    }
+
+    /**
+     * This sample demonstrates an indexed filter that returns digits whose name is
+     * shorter than their value.
+
+     * <strong>NOTE</strong>: Needs full conversion.
+     */
+    public void lambda5() {
+        System.out.println("\nShort digits:");
+        List<String> digits = Arrays.asList("zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine");
+        IndexHolder i = new IndexHolder();
+        digits.stream()
+                .filter(x -> x.length() < i.postIncrement())
+                .forEach(x -> System.out.println(x));
+    }
+
+}

src/main/java/com/drunkendev/lambdas/helper/IndexHolder.java

@@ -0,0 +1,58 @@
+/*
+ * IndexHolder.java    Feb 2 2014, 03:34
+ *
+ * Copyright 2014 Drunken Dev.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.drunkendev.lambdas.helper;
+
+
+/**
+ * Represents an index to allow for incrementing/decrementing within a lambda
+ * context as only (effective) final variables may be altered.
+ *
+ * @author  Brett Ryan
+ */
+public class IndexHolder {
+
+    private int index;
+
+    /**
+     * Creates a new {@code IndexHolder} instance.
+     */
+    public IndexHolder() {
+    }
+
+    public int getIndex() {
+        return index;
+    }
+
+    public int preIncrement() {
+        return ++index;
+    }
+
+    public int postIncrement() {
+        return index++;
+    }
+
+    public int preDecrement() {
+        return --index;
+    }
+
+    public int postDecrement() {
+        return index--;
+    }
+
+}