第三章示例代码

Author: ipofss

src/main/java/com/wbs/java8lambda/chapter3/AppleComparator.java

@@ -0,0 +1,19 @@
+package com.wbs.java8lambda.chapter3;
+
+import com.wbs.java8lambda.entity.Apple;
+
+import java.util.Comparator;
+
+/**
+ * TODO
+ *
+ * @author: wangbingshuai
+ * @create: 2019-10-30 15:17
+ **/
+public class AppleComparator implements Comparator<Apple> {
+
+    @Override
+    public int compare(Apple o1, Apple o2) {
+        return o1.getWeight().compareTo(o2.getWeight());
+    }
+}

src/main/java/com/wbs/java8lambda/chapter3/ApplePredicate.java

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+package com.wbs.java8lambda.chapter3;
+
+import com.wbs.java8lambda.entity.Apple;
+
+/**
+ * TODO
+ *
+ * @author: wangbingshuai
+ * @create: 2019-10-30 15:31
+ **/
+@FunctionalInterface
+public interface ApplePredicate {
+    boolean test(Apple a);
+}

src/main/java/com/wbs/java8lambda/chapter3/BufferedReaderProcessor.java

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+package com.wbs.java8lambda.chapter3;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+
+/**
+ * TODO
+ *
+ * @author: wangbingshuai
+ * @create: 2019-10-30 15:52
+ **/
+@FunctionalInterface
+public interface BufferedReaderProcessor {
+    String process(BufferedReader br) throws IOException;
+}

src/main/java/com/wbs/java8lambda/chapter3/ExecuteAround.java

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+package com.wbs.java8lambda.chapter3;
+
+import java.io.BufferedReader;
+import java.io.FileReader;
+import java.io.IOException;
+
+/**
+ * TODO
+ *
+ * @author: wangbingshuai
+ * @create: 2019-10-30 15:42
+ **/
+public class ExecuteAround {
+    public static void main(String[] args) throws IOException {
+        String result = processFileLimited();
+        System.out.println(result);
+
+        System.out.println("---");
+
+        String oneLine = processFile((BufferedReader b) -> b.readLine());
+        System.out.println(oneLine);
+
+        System.out.println("---");
+
+        String twoLine = processFile((BufferedReader br) -> br.readLine() + br.readLine());
+        System.out.println(twoLine);
+    }
+
+    private static String processFileLimited() throws IOException {
+        // 这里的相对路径不管用的话，需要改成绝对路径
+        try (BufferedReader br = new BufferedReader(new FileReader("lambdasinaction/chap3/data.txt"))) {
+            return br.readLine();
+        }
+    }
+
+    private static String processFile(BufferedReaderProcessor p) throws IOException {
+        try (BufferedReader br = new BufferedReader(new FileReader("lambdasinaction/chap3/data.txt"))) {
+            return p.process(br);
+        }
+    }
+}

src/main/java/com/wbs/java8lambda/chapter3/Lambdas.java

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+package com.wbs.java8lambda.chapter3;
+
+import com.wbs.java8lambda.entity.Apple;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.List;
+
+/**
+ * TODO
+ *
+ * @author: wangbingshuai
+ * @create: 2019-10-30 15:29
+ **/
+public class Lambdas {
+    public static void main(String[] args) {
+        Runnable r = () -> System.out.println("Hello!");
+        r.run();
+
+        List<Apple> list = Arrays.asList(new Apple(80, "green"),
+                new Apple(155, "green"),
+                new Apple(120, "red"));
+        List<Apple> greenApples = filter(list, (Apple a) -> "green".equals(a.getColor()));
+        System.out.println(greenApples);
+
+        Comparator<Apple> c = (Apple o1, Apple o2) -> o1.getWeight().compareTo(o2.getWeight());
+        list.sort(c);
+        System.out.println(list);
+    }
+
+    private static List<Apple> filter(List<Apple> list, ApplePredicate p) {
+        List<Apple> result = new ArrayList<>();
+        for (Apple apple : list) {
+            if (p.test(apple)) {
+                result.add(apple);
+            }
+        }
+        return result;
+    }
+}

src/main/java/com/wbs/java8lambda/chapter3/Sorting.java

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+package com.wbs.java8lambda.chapter3;
+
+import com.wbs.java8lambda.entity.Apple;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.List;
+
+/**
+ * TODO
+ *
+ * @author: wangbingshuai
+ * @create: 2019-10-30 15:11
+ **/
+public class Sorting {
+    public static void main(String[] args) {
+        List<Apple> list = new ArrayList<>();
+        list.addAll(Arrays.asList(new Apple(80, "green"),
+                new Apple(155, "green"),
+                new Apple(120, "red")));
+
+        list.sort(new AppleComparator());
+        System.out.println(list);
+
+        list.set(1, new Apple(30, "green"));
+        list.sort(new Comparator<Apple>() {
+            @Override
+            public int compare(Apple o1, Apple o2) {
+                return o1.getWeight().compareTo(o2.getWeight());
+            }
+        });
+        System.out.println(list);
+
+        list.set(1, new Apple(20, "red"));
+        list.sort((o1, o2) -> o1.getWeight().compareTo(o2.getWeight()));
+        System.out.println(list);
+
+        list.set(1, new Apple(10, "red"));
+        list.sort(Comparator.comparing(Apple::getWeight));
+        System.out.println(list);
+    }
+}

src/main/resources/lambdasinaction/chap3/data.txt

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+Java
+8
+Lambdas
+In
+Action

src/main/resources/lambdasinaction/chap5/data.txt

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+The quick brown fox jumped over the lazy dog
+The lazy dog jumped over the quick brown fox