Thinking in java-32 Iterable & Iterator Inteface

1. java中的Iterable & Iterator?

Q1: What are the difference between Iterator VS Iterable?
A1: The “Iterable” was introduced to be able to use in the ‘foreach’ loop. A class implementing the Iterable interface can be iterated over.
实现了 Iterable接口的类可以用于增强的for循环中国年，即：for-each语句。

2. for-each 和 iterable

foreach->iterator()->next()

3. Iterator()

迭代器Iterator是这样一类东西：它管理可迭代对象的迭代访问。它维护一个当前访问迭代的状态，而且知道下一个元素的位置以及如何得到它。

Q2: How to get an Iterable in java 8 to be used in a foreach loop?
A2: In java 8, call the double ‘::’ notation as below, you can get an iterable from the Stream.

package com.fqy.blog;import java.net.URL;import java.nio.charset.StandardCharsets;import java.nio.file.Files;import java.nio.file.Path;import java.nio.file.Paths;import java.util.stream.Stream;public class MyFileReader {    public static void main(String[] args) {        Path file = null;        try {            // read from the classpath            URL url = MyFileReader.class.getResource("readme.txt");            file = Paths.get(url.toURI());            // Java 8: Stream class            Stream<String> lines = Files.lines(file, StandardCharsets.UTF_8);            for (String line : (Iterable<String>) lines::iterator) {                System.out.println("read=" + line);            }        } catch (Exception e) {            e.printStackTrace();        }    }}//Running result:read=You can rewind an Iterable by getting a new iterator() from the Iterable. read=But an Iterator only has the next() method. read=So, an Iterable is handy if you want to traverse the elements more than once.read=read=Q2. How do you get an Iterable in Java 8 to be used in a foreach loop?read=A2. In Java 8, when you call the double “::” notation as shown below, you get an Iterable from the Stream.

4. Using both Iterable and Iterator

package com.fqy.blog;import java.util.Iterator;class MyIterable<T> implements Iterable<T> {    public T[] arr = null;    public MyIterable(T[] arr) {        this.arr = arr;    }    @Override    public Iterator<T> iterator() {        return new Iterator<T>() {            private int index = 0;            @Override            public boolean hasNext() {                if (index < arr.length)                    return true;                return false;            }            @Override            public T next() {                System.out.println("Invoking next: ");                if (this.hasNext())                    return arr[index++];                return null;            }            @Override            public void remove() {                throw new UnsupportedOperationException();            }        };    }}public class IterableWithIterator {    public static void main(String[] args) {        String[] arr = { "Java", "Oracle", "Operation System", "Spring MVC" };        MyIterable<String> myIterable = new MyIterable<>(arr);        for (String str : myIterable)            System.out.println(str);    }}//Running result:Invoking next: JavaInvoking next: OracleInvoking next: Operation SystemInvoking next: Spring MVC