lambda expressions demo

Author: Sergey Lukichev

Drafts/LambdaDemo/.gitignore

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+/target/
+!.mvn/wrapper/maven-wrapper.jar
+
+### STS ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+
+### IntelliJ IDEA ###
+.idea
+*.iws
+*.iml
+*.ipr
+
+### NetBeans ###
+/nbproject/private/
+/build/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/

Drafts/LambdaDemo/src/Demo.java

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+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.function.Consumer;
+import java.util.function.Function;
+import java.util.function.Predicate;
+import java.util.function.Supplier;
+
+public class Demo {
+    public static void main(String[] args) {
+        Comparator<String> c = new Comparator<String>() {
+            @Override
+            public int compare(String o1, String o2) {
+                return 0;
+            }
+        };
+
+        DemoIntterface demo = new DemoImpl();
+
+        System.out.println(demo.trasform(5));
+
+
+        String someString = DemoIntterface.SOME_STRING;
+
+        DemoIntterface dia = new DemoIntterface() {
+            @Override
+            public String getString(int i) {
+                return String.valueOf(i);
+            }
+        };
+
+        DemoIntterface di = (a) -> String.valueOf(a);
+
+        //"abc" -> 3
+        Function<String, Integer> f1 = (s) -> s.length();
+
+        // 5 -> 25
+
+        Function<Integer, Integer> f2 = (a) -> a * a;
+
+        Predicate<String> f3 = (s) -> s.length() % 2 == 0;
+
+        Consumer<String> f4 = (s) -> System.out.println(s);
+
+        Supplier<Integer> f5 = () -> (int)(Math.random());
+
+
+//        {
+//          if(s.length() % 2 == 0) return true;
+//          else return false;
+//        };
+
+        Function<Integer, Integer> ff1 = (a) -> a*a;
+        doSomeMath(ff1, 10);
+
+        Function<Integer, Integer> ff2 = (a) -> a*10;
+        doSomeMath(ff2, 24);
+
+        Function<Integer, Integer> ff3 = Demo::getInt;
+        doSomeMath(ff3, 56);
+
+        Function<String, String> getString = Demo::getString;
+
+        Function<String, String> getStringL = (s) -> s;
+
+        transformString((s) -> s, "abc");
+        transformString(Demo::getString, "abc");
+
+
+        Function<String, String> type = Person::type;
+
+        Person p = new Person("Ivan");
+
+        Supplier<String> getName = p::getName;
+
+        System.out.println(getName.get());
+
+        Function<Person, String> getName1 = Person::getName;
+
+        System.out.println(getName1.apply(p));
+
+        Supplier<Person> person = Person::new;
+
+    }
+
+    public static int getInt(int a) {
+        return a%2==0 ? 1: -1;
+    }
+
+    public static String transformString(Function<String, String> f, String s) {
+        return f.apply(s);
+
+    }
+
+    public static int doSomeMath(Function<Integer, Integer> f, int a) {
+        System.out.println(a);
+        return f.apply(a);
+    }
+
+    public static String getString(String input) {
+        return input;
+    }
+}

Drafts/LambdaDemo/src/DemoImpl.java

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+public class DemoImpl implements DemoIntterface {
+
+    int anInt;
+
+    @Override
+    public String getString(int i) {
+        return String.valueOf(i);
+    }
+
+    @Override
+    public String trasform(int i) {
+        anInt = 3;
+        return "Hello World " + i + anInt;
+    }
+}

Drafts/LambdaDemo/src/DemoIntterface.java

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+@FunctionalInterface
+public interface DemoIntterface {
+    String SOME_STRING = "Hello";
+
+    String getString(int i);
+    //String transform(int i);
+
+    default String trasform(int i) {
+        return "Hello World";
+    }
+}

Drafts/LambdaDemo/src/Person.java

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+public class Person {
+    private String name;
+
+    public Person() {
+    }
+
+    public Person(String name) {
+        this.name = name;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public static String type(String s) {
+        return "HUMAN";
+    }
+
+    @Override
+    public String toString() {
+        return "Person{" +
+                "name='" + name + '\'' +
+                '}';
+    }
+}