JSONObject obj = new JSONObject();
obj.put(key, value);

import org.json.JSONObject;

public class JSONObjectSample {

  public static void main(String[] args) {
    createJson();
  }

  private static void createJson() {
    JSONObject obj = new JSONObject();
    obj.put("name", "John");
    obj.put("sex", "male");
    obj.put("age", 22);
    obj.put("is_student", true);
    obj.put("hobbies", new String[] {"hiking", "swimming"});
    //调用toString()方法可直接将其内容打印出来
    System.out.println(obj.toString());
  }

}

{"hobbies":["hiking","swimming"],"sex":"male","name":"John","is_student":true,"age":22}

public class JSONObjectSample {

  public static void main(String[] args) {
    createJsonByMap();
  }

  private static void createJsonByMap() {
    Map<String, Object> data = new HashMap<String, Object>();
    data.put("name", "John");
    data.put("sex", "male");
    data.put("age", 22);
    data.put("is_student", true);
    data.put("hobbies", new String[] {"hiking", "swimming"});
    
    JSONObject obj = new JSONObject(data);
    System.out.println(obj.toString());
  }

}

public class PersonInfo {

  private String name;
  private String sex;
  private int age;
  private boolean isStudent;
  private String[] hobbies;
  
  public void setName(String name) {
    this.name = name;
  }
  public void setSex(String sex) {
    this.sex = sex;
  }
  public void setAge(int age) {
    this.age = age;
  }
  public void setStudent(boolean isStudent) {
    this.isStudent = isStudent;
  }
  public void setHobbies(String[] hobbies) {
    this.hobbies = hobbies;
  }
    //getter不能少
  public String getName() {
    return name;
  }
  public String getSex() {
    return sex;
  }
  public int getAge() {
    return age;
  }
  public boolean isStudent() {
    return isStudent;
  }
  public String[] getHobbies() {
    return hobbies;
  }
}

import org.json.JSONObject;

public class JSONObjectSample {

  public static void main(String[] args) {
    createJsonByJavaBean();
  }

  private static void createJsonByJavaBean() {
    PersonInfo info = new PersonInfo();
    info.setName("John");
    info.setSex("male");
    info.setAge(22);
    info.setStudent(true);
    info.setHobbies(new String[] {"hiking", "swimming"});
    
    JSONObject obj = new JSONObject(info);
    System.out.println(obj);
  }

}

{
 "hobbies": [
  "hiking",
  "swimming"
 ],
 "sex": "male",
 "name": "John",
 "is_student": true,
 "age": 22
}

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
 <modelVersion>4.0.0</modelVersion>

 <groupId>com.studying</groupId>
 <artifactId>myjson</artifactId>
 <version>0.0.1-SNAPSHOT</version>
 <packaging>jar</packaging>

 <name>myjson</name>
 <url>http://maven.apache.org</url>

 <properties>
  <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 </properties>

 <dependencies>
  <dependency>
   <groupId>org.json</groupId>
   <artifactId>json</artifactId>
   <version>20160810</version>
  </dependency>
  <!--加入对commons-io的依赖-->
  <dependency>
   <groupId>commons-io</groupId>
   <artifactId>commons-io</artifactId>
   <version>2.4</version>
  </dependency>
 </dependencies>
</project>

import java.io.File;
import java.io.IOException;

import org.apache.commons.io.FileUtils;
import org.json.JSONArray;
import org.json.JSONObject;

public class JSONObjectSample {

  public static void main(String[] args) throws IOException {
    File file = new File("src/main/java/demo.json");
    String content = FileUtils.readFileToString(file);
    //对基本类型的解析
    JSONObject obj = new JSONObject(content);
    System.out.println("name：" + obj.getString("name"));
    System.out.println("sex：" + obj.getString("sex"));
    System.out.println("age" + obj.getInt("age"));
    System.out.println("is_student" + obj.getBoolean("is_student"));
    //对数组的解析
    JSONArray hobbies = obj.getJSONArray("hobbies");
    System.out.println("hobbies：");
    for (int i = 0; i < hobbies.length(); i++) {
      String s = (String) hobbies.get(i);
      System.out.println(s);
    }
  }
}