第九天 JSON解析、集合

JSON

生成JSON

方法一

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;
public class JSONTest {
    public static void main(String[] args) {
        Student zhangsan=new Student(20,"張三");
        Student lisi=new Student(20,"李四");
        Student xiaoming=new Student(20,"小明");
        JSONObject obj=new JSONObject();
        JSONArray array=new JSONArray();
        array.add(zhangsan);
        array.add(lisi);
        array.add(xiaoming);
        obj.put("clazz", array);
        System.out.println(obj.toString());     
    }
}

方法二

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;
public class JSONTest {
    public static void main(String[] args) {
        JSONObject obj1=new JSONObject();
        JSONObject obj2=new JSONObject();
        JSONObject obj3=new JSONObject();
        obj1.put("name", "張三");
        obj2.put("name", "李四");
        obj3.put("name", "小明");
        JSONArray array=new JSONArray();
        array.add(obj1);
        array.add(obj2);
        array.add(obj3);
        JSONObject clazz =new JSONObject();
        clazz.put("clazzname","163");
        clazz.put("student", array);
        clazz.put("studentNum", "3");
        System.out.println(clazz.toString());

JSON 解析

package com.baidu.test;
import java.io.File;
import net.sf.json.JSONArray;
import net.sf.json.JSONObject;
public class JSONTest {
    public static void main(String[] args) {
        File file=new File("d:\\1.txt");
        String json=creatJson();
        if(json!=null){
            JSONObject clazz=JSONObject.fromObject(json);
            System.out.println(clazz.getString("clazzname"));
            JSONArray array=clazz.getJSONArray("student");
            for(int i=0;i<array.size();i++){
                JSONObject obj=array.getJSONObject(i);
                System.out.println(obj.getString("name"));
            }
        }   
    }
    public static String  creatJson (){
        JSONObject obj1=new JSONObject();
        JSONObject obj2=new JSONObject();
        JSONObject obj3=new JSONObject();
        obj1.put("name", "張三");
        obj2.put("name", "李四");
        obj3.put("name", "小明");
        JSONArray array=new JSONArray();
        array.add(obj1);
        array.add(obj2);
        array.add(obj3);
        JSONObject clazz =new JSONObject();
        clazz.put("clazzname","163");
        clazz.put("student", array);
        clazz.put("studentNum", "3");
        System.out.println(clazz.toString());
        return clazz.toString();
    }
}

獲得日期、時間

import java.util.Calendar;
import java.util.Date;
public class DateTime {
    public static void main(String[] args) {
        Date date=new Date();
        System.out.println("系統當前時間："+date);
        System.out.println("從1970年到現在的毫秒數："+date.getTime());
        Calendar calendar=Calendar.getInstance();//Calendar是一個抽象類， 提供了一個類方法 getInstance，以獲得此類型的一個通用的對象
        System.out.println("現在是"+calendar.get(Calendar.DAY_OF_MONTH)+"號");
        System.out.println("現在是第"+calendar.get(Calendar.WEEK_OF_MONTH)+"周");
        calendar.add(Calendar.DAY_OF_MONTH, 6);
        System.out.println("六天之後是"+calendar.get(Calendar.DAY_OF_MONTH)+"號");
        System.out.println("六天之後是第"+calendar.get(Calendar.WEEK_OF_MONTH)+"周");
    }
}

package com.baidu.test;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;
public class DateTime {
    public static void main(String[] args) {
        Date date=new Date();
        SimpleDateFormat format=new SimpleDateFormat("yyyy/MM/dd   kk:mm:ss");
        System.out.println(format.format(date));
        TimeZone zone=TimeZone.getDefault();
        System.out.println(zone);
        System.out.println(zone.getID());   
    }
}

package com.baidu.test;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
public class DateTime {
    public static void main(String[] args) {
        SimpleDateFormat format=new SimpleDateFormat("yyyy/MM/dd   kk:mm:ss");
        String s="2015/10/24   11:44:20";
        try {
            Date date1=format.parse(s);
            System.out.println("秒數是："+date1.getSeconds());//20
            System.out.println("年數是"+date1.getYear());//115:從1900年算起
        } catch (ParseException e) {
            e.printStackTrace();
        }
    }
}

集合

隨機生成10個數

方法一

package com.baidu.test;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Random;
public class Test2 {
    public static void main(String[] args) {
        HashSet<Integer> set=new HashSet<Integer>();
        Random random =new Random();
        while(set.size()<10){
            int i=random.nextInt(90)+10;
            set.add(i);
        }
        Iterator it=set.iterator();
        while(it.hasNext()){
            System.out.print(it.next()+"\t");
        }

方法二

package com.baidu.test;
import java.util.ArrayList;
import java.util.Random;
public class Test2 {
    public static void main(String[] args) {
    ArrayList<Integer> list=new ArrayList<Integer>();
        Random random1 =new Random();
        while(list.size()<10){
            int i=random1.nextInt(90)+10;
            if(!list.contains(i)){
                list.add(i);
            }
            System.out.println(i);
        }
    }
}

package com.baidu.test;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Set;
public class Test2 {
    public static void main(String[] args) {
        HashMap<String,Student> clazz =new HashMap<String,Student>();
        clazz.put("zhangsan", new Student(20,"張三"));
        clazz.put("lisi", new Student(22,"李四"));
        clazz.put("xiaoming", new Student(21,"小明"));
        Set<String> keys=clazz.keySet();
        System.out.println(clazz.get("zhangsan").getName());
        Iterator<String> it=keys.iterator();
        while(it.hasNext()){
            String key=it.next();
            System.out.println(key+"------"+clazz.get(key).getName());
        }
    }
}

按年齡順序輸出

package com.baidu.test;
import java.util.Comparator;
public class StudentComparator implements Comparator<Student> {
    @Override
    public int compare(Student s1, Student s2) {
        return s1.getAge()-s2.getAge();
    }
}

package com.baidu.test;
import java.util.List;
import java.util.ArrayList;
import java.util.Collections;
public class Test1 {
    public static void main(String[] args) {
        List<Student> students=new ArrayList<Student>();
        Student zhangsan=new Student(20,"張三");
        students.add(zhangsan);
        Student lisi=new Student(22,"李四");
        students.add(lisi);
        Student xiaoming=new Student(21,"小明");
        students.add(xiaoming);
        Collections.sort(students, new StudentComparator());
        for(int i=0;i<students.size();i++){
            Student s=students.get(i);
        System.out.println(s.getName()+s.getAge());
        }

        //遍歷的另一種方式
        for(Student s:students){
            System.out.println(s.getName());
        }
    }
}

枚舉

package com.baidu.test;
public enum Sex {
    MALE,FEMALE
}

泛型

public class Student<T>//T:類型不確定，泛型