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hellokatonhellokaton
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🍱 update default method video url
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‎README.md‎

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@@ -25,7 +25,7 @@ java 8 改变了我们思考和编码的方式，在这里你可以学习到 Jav
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|第 3 课 | [理解 lambda](https://github.com/biezhi/learn-java8/blob/master/java8-lambda/README.md) | [哔哩哔哩](https://www.bilibili.com/video/av19287893/index_3.html#page=3) ¦ [Youtube](https://youtu.be/VkdMeFEGDH8) | [lambda1](https://github.com/biezhi/learn-java8/tree/master/java8-lambda/src/main/java/io/github/biezhi/java8/lambda/lesson1) |
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|第 4 课 | [初尝 lambda](https://github.com/biezhi/learn-java8/blob/master/java8-lambda/README.md) | [哔哩哔哩](https://www.bilibili.com/video/av19287893/index_4.html#page=4) ¦ [Youtube](https://youtu.be/X7Zv5vygjTc) | [lambda2](https://github.com/biezhi/learn-java8/tree/master/java8-lambda/src/main/java/io/github/biezhi/java8/lambda/lesson2) |
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|第 5 课 | [lambda 进阶](https://github.com/biezhi/learn-java8/blob/master/java8-lambda/README.md) | [哔哩哔哩](https://www.bilibili.com/video/av19287893/index_5.html#page=5) ¦ [Youtube](https://youtu.be/3G83it4IASc) | [lambda3](https://github.com/biezhi/learn-java8/tree/master/java8-lambda/src/main/java/io/github/biezhi/java8/lambda/lesson3) |
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|第 6 课 | 默认方法的妙用 | 哔哩哔哩 ¦ Youtube | |
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|第 6 课 | 默认方法的妙用 | [哔哩哔哩](https://www.bilibili.com/video/av19287893/index_6.html#page=6) ¦ [Youtube](https://youtu.be/sAuEnkWezDM) | [lambda3](https://github.com/biezhi/learn-java8/tree/master/java8-default-methods/src/main/java/io/github/biezhi/java8/defaultmethods) |
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|第 7 课 | 干掉空指针之 Optional | 哔哩哔哩 ¦ Youtube | |
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|第 8 课 | 理解 Stream | 哔哩哔哩 ¦ Youtube | |
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|第 9 课 | Stream API（上）| 哔哩哔哩 ¦ Youtube | |

‎java8-default-methods/src/main/java/io/github/biezhi/java8/defaultmethods/Calculator.java‎

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@@ -16,4 +16,11 @@ public interface Calculator {
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int divide(int number, int divisor);
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default int mod(int first, int second){
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return first % second;
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}
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static Calculator getInstance(){
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return new BasicCalculator();
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}
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}

‎java8-default-methods/src/main/java/io/github/biezhi/java8/defaultmethods/CalculatorFactoy.java‎

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@@ -0,0 +1,13 @@
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package io.github.biezhi.java8.defaultmethods;
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/**
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* @author biezhi
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* @date 2018/2/11
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*/
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public class CalculatorFactoy {
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public static Calculator getInstance(){
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return new BasicCalculator();
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}
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}

‎java8-default-methods/src/main/java/io/github/biezhi/java8/defaultmethods/Collection.java‎

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package io.github.biezhi.java8.defaultmethods;
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import java.util.Iterator;
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import java.util.function.Predicate;
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/**
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* @author biezhi
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* @date 2018/2/11
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*/
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public interface Collection<T> extends java.util.Collection {
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default boolean removeIf2(Predicate<T> predicate){
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boolean isRemoved = false;
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Iterator<T> iterator = iterator();
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while(iterator.hasNext()){
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if(predicate.test(iterator.next())){
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iterator.remove();
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isRemoved = true;
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}
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}
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return isRemoved;
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}
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}

‎java8-default-methods/src/main/java/io/github/biezhi/java8/defaultmethods/UseCalc.java‎

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@@ -12,8 +12,10 @@ public static void main(String[] args) {
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int sum = calculator.add(1, 2);
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System.out.println(sum);
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BasicCalculator cal = new BasicCalculator();
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Calculator cal = Calculator.getInstance();
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int difference = cal.subtract(3, 2);
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System.out.println(difference);
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System.out.println(cal.mod(3, 2));
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}
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}

‎java8-optional/src/main/java/io/github/biezhi/java8/optional/OptionalDemo.java‎

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package io.github.biezhi.java8.optional;
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import java.util.Optional;
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import java.util.Properties;
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/**
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* @author biezhi
@@ -36,12 +37,64 @@ public void map() {
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public void flatMap() {
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User user = new User();
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Optional<User> userOptional = Optional.of(user);
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// userOptional.map(User::getOptAddress).map(Address::getStreet);
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userOptional.flatMap(User::getOptAddress).map(Address::getStreet);
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// userOptional.map(user -> user.getOptAddress())
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Optional<String> stringOptional = userOptional.flatMap(User::getOptAddress).map(Address::getStreet);
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}
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/**
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* 4. 默认行为及解引用 Optional 对象
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*/
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public void defaultValue() {
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Optional<Address> addressOptional = Optional.ofNullable(null);
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String street = addressOptional.map(Address::getStreet).orElse("北京二环");
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System.out.println(street);
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}
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public static void main(String[] args) {
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User user = new User();
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user.setUsername("biezhi");
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user.setPassword("123456");
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user.setOptAddress(Optional.of(new Address("达尔文路", "88号")));
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user.setAge(30);
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// Address address1 = null;
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// try {
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// address1 = user.getOptAddress().filter(address -> address.getDoor().contains("878"))
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// .orElseThrow(new Supplier<Throwable>() {
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// @Override
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// public Throwable get() {
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// return new Exception("挂了");
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// }
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// });
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// } catch (Throwable throwable) {
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// throwable.printStackTrace();
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// }
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// System.out.println(address1);
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System.out.println(getStreet(Optional.of(user), 50));
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}
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public static String getStreet(Optional<User> user, int minAge) {
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return user.filter(u -> u.getAge() >= minAge)
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.flatMap(User::getOptAddress)
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.map(Address::getStreet)
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.orElse("没有");
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}
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public static Optional<Integer> parseInt(String value) {
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try {
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return Optional.ofNullable(Integer.parseInt(value));
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} catch (Exception e) {
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return Optional.empty();
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}
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}
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public int readPoint(Properties props, String name) {
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return Optional.ofNullable(props.getProperty(name))
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.flatMap(OptionalDemo::parseInt)
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.filter(i -> i > 0)
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.orElse(0);
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}
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}

‎java8-optional/src/main/java/io/github/biezhi/java8/optional/User.java‎

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@@ -15,6 +15,7 @@ public class User {
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private String username;
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private String password;
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private Integer age;
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private Address address;
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private Optional<Address> optAddress;

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