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XGerryXGerry
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Java Basic Study
0 parents  commit 643264c

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‎.gitignore‎

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# Created by .ignore support plugin (hsz.mobi)
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### Example user template template
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### Example user template
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# IntelliJ project files
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.idea
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*.iml
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out
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gen

‎src/ArrayListDemo.java‎

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import java.util.ArrayList;
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import java.util.Iterator;
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import java.util.List;
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public class ArrayListDemo {
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public static void main(String[] args) {
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List<String> list = new ArrayList<>();
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list.add("Hello");
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list.add("World");
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list.add("Haha");
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//第一种遍历方法使用foreach遍历List
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for (int i = 0; i < list.size(); i++) {
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System.out.println(list.get(i));
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}
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for (String str :
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list) {
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System.out.println(str);
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}
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//第二种遍历，把链表变为数组相关的内容进行遍历
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String[] strArray = new String[list.size()];
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list.toArray(strArray);
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for (int i = 0; i < strArray.length; i++) {
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System.out.println(strArray[i]);
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}
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for (String str :
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strArray) {
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System.out.println(str);
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}
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//第三种遍历 使用迭代器进行相关遍历
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Iterator<String> iterator = list.iterator();
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while (iterator.hasNext()) {
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System.out.println(iterator.next());
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}
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}
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}

‎src/BRReadDemo.java‎

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import java.io.BufferedReader;
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import java.io.IOException;
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import java.io.InputStreamReader;
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public class BRReadDemo {
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public static void main(String[] args) throws IOException {
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BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
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System.out.println("Enter lines of text.");
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System.out.println("Enter 'end' to quit.");
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String str;
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do {
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str = br.readLine();
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System.out.println(str);
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} while (!str.equals("end"));
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}
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}

‎src/DateDemo.java‎

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import java.text.SimpleDateFormat;
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import java.time.Instant;
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import java.time.LocalDate;
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import java.time.LocalDateTime;
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import java.time.LocalTime;
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import java.util.Date;
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public class DateDemo {
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public static void main(String[] args) {
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Date date = new Date();
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SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
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System.out.println(simpleDateFormat.format(date));
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Instant instant = Instant.now();
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System.out.println(instant);
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Instant instant1 = Instant.ofEpochSecond(20);
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System.out.println(instant1);
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Instant instant2 = Instant.ofEpochSecond(30, 100);
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System.out.println(instant2);
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Instant instant3 = Instant.ofEpochMilli(1000);
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System.out.println(instant3);
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LocalDate localDate = LocalDate.now();
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System.out.println(localDate);
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LocalDate localDate1 = LocalDate.of(2017, 7, 22);
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System.out.println(localDate1);
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LocalDate localDate2 = LocalDate.ofYearDay(2018, 100);
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System.out.println(localDate2);
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LocalDate localDate3 = LocalDate.ofEpochDay(10);
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System.out.println(localDate3);
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LocalDateTime localDateTime = LocalDateTime.now();
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System.out.println(localDateTime);
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LocalTime localTime = LocalTime.now();
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System.out.println(localTime);
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System.out.println(date.getTime());
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}
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}

‎src/Employee.java‎

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public class Employee {
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String name;
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int age;
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String designation;
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double salary;
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public Employee(String name)
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{
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this.name=name;
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}
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public void setAge(int age) {
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this.age = age;
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}
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public void setDesignation(String designation) {
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this.designation = designation;
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}
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public void setSalary(double salary) {
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this.salary = salary;
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}
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public void printEmployee()
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{
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System.out.println("名字"+name);
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System.out.println("年龄"+age);
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System.out.println("职位"+designation);
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System.out.println("薪水"+salary);
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}
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}

‎src/ExceptionDemo.java‎

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public class ExceptionDemo {
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public static void main(String[] args) {
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try {
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System.out.println(10 / 0);
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} catch (Exception ex) {
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ex.printStackTrace();
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}
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}
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}

‎src/FileStreamTest.java‎

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import java.io.*;
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public class FileStreamTest {
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public static void main(String[] args) throws IOException {
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/* int bWrite[] = {11, 21, 3, 666};
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OutputStream outputStream=new FileOutputStream("test.txt");
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for (int i = 0; i <bWrite.length ; i++) {
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outputStream.write(bWrite[i]);
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}
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outputStream.close();
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InputStream is = new FileInputStream("test.txt");
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int size = is.available();
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for (int i = 0; i < size; i++) {
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System.out.print((char) is.read() + " ");
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}
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is.close();*/
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File file=new File("a.txt");
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FileOutputStream fop =new FileOutputStream(file);
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OutputStreamWriter writer = new OutputStreamWriter(fop, "UTF-8");
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// 构建OutputStreamWriter对象,参数可以指定编码,默认为操作系统默认编码,windows上是gbk
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writer.append("中文输入");
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// 写入到缓冲区
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writer.append("\r\n");
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// 换行
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writer.append("English");
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// 刷新缓存冲,写入到文件,如果下面已经没有写入的内容了,直接close也会写入
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writer.close();
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// 关闭写入流,同时会把缓冲区内容写入文件,所以上面的注释掉
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fop.close();
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// 关闭输出流,释放系统资源
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FileInputStream fip = new FileInputStream(file);
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// 构建FileInputStream对象
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InputStreamReader reader = new InputStreamReader(fip, "UTF-8");
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// 构建InputStreamReader对象,编码与写入相同
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StringBuffer sb = new StringBuffer();
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while (reader.ready()) {
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sb.append((char) reader.read());
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// 转成char加到StringBuffer对象中
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}
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System.out.println(sb.toString());
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reader.close();
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// 关闭读取流
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fip.close();
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// 关闭输入流,释放系统资源
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}
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}

‎src/GenericMethodDemo.java‎

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public class GenericMethodDemo {
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public static void main(String[] args) {
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String[] strArray = {"11", "22", "33"};
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Integer[] intArray = {1, 2, 3};
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Character[] charArray = {'H', 'E', 'L', 'L', 'O'};
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Double[] doubleArray = {1.1, 2.2, 3.3};
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System.out.println("\n字符串数组元素为:");
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printArray(strArray); // 传递一个字符串数组
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System.out.println("\n整型数组元素为:");
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printArray(intArray); // 传递一个整型数组
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System.out.println("\n双精度型数组元素为:");
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printArray(doubleArray); // 传递一个双精度型数组
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System.out.println("\n字符型数组元素为:");
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printArray(charArray); // 传递一个字符型数组
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}
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public static <T> void printArray(T[] inputArray) {
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for (T element : inputArray
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) {
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System.out.printf("%s ", element);
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}
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System.out.println();
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}
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}

‎src/HelloWorld.java‎

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public class HelloWorld {
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public static void main(String[] args) {
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System.out.println("Hello World!");
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}
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}

‎src/MapDemo.java‎

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import java.util.HashMap;
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import java.util.Iterator;
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import java.util.Map;
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public class MapDemo {
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public static void main(String[] args) {
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Map<String, String> map = new HashMap<>();
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map.put("1", "Value1");
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map.put("2", "Value2");
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map.put("3", "Value3");
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//第一种：普遍使用，二次取值
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System.out.println("通过Map.keySet遍历key和value：");
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for (String key :
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map.keySet()) {
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System.out.println(key);
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}
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for (String value :
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map.values()) {
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System.out.println(value);
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}
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//第二种
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System.out.println("通过Map.entrySet使用iterator遍历key和value：");
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Iterator<Map.Entry<String, String>> iterator = map.entrySet().iterator();
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while (iterator.hasNext()) {
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Map.Entry<String, String> entry = iterator.next();
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System.out.println("key=" + entry.getKey() + " and value=" + entry.getValue());
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}
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//第三种：推荐，尤其是容量大时
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System.out.println("通过Map.entrySet遍历key和value");
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for (Map.Entry<String, String> entry : map.entrySet()
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) {
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System.out.println("key=" + entry.getKey() + " and value=" + entry.getValue());
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}
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}
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}

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