10 Nov 2017

java 常用方法

list转数组

public static Object[] List2Array(List<Object> oList) {   
     Object[] oArray = oList.toArray(new Object[] {});   
     // TODO 需要在用到的时候另外写方法，不支持泛型的Array.   
     return oArray;   
 }

set转数组

 public static Object[] Set2Array(Set<Object> oSet) {   
     Object[] oArray = oSet.toArray(new Object[] {});
     // Object[] oArray = oSet.toArray(new Object[0]);   
     // TODO 需要在用到的时候另外写方法，不支持泛型的Array.   
     return oArray;   
 }

set转list

 public static <T extends Object> List<T> Set2List(Set<T> oSet) {   
     List<T> tList = new ArrayList<T>(oSet);   
     // TODO 需要在用到的时候另外写构造，根据需要生成List的对应子类。   
     return tList;   
 }

数组转List

public static <T extends Object> List<T> Array2List(T[] tArray) {   
     List<T> tList = Arrays.asList(tArray);   
     // asList()返回的tList无法add(),remove(),clear()等影响集合个数操作，   
     List<T> tList = new ArrayList<T>(Arrays.asList(tArray));   
     return tList;   
 }

List转Set

 public static <T extends Object> Set<T> List2Set(List<T> tList) {   
 Set<T> tSet = new HashSet<T>(tList);   
 //TODO 具体实现看需求转换成不同的Set的子类。   
 return tSet;   
 }

Array转Set

 public static <T extends Object> Set<T> Array2Set(T[] tArray) {   
     Set<T> tSet = new HashSet<T>(Arrays.asList(tArray));   
     // TODO 没有一步到位的方法，根据具体的作用，选择合适的Set的子类来转换。   
     return tSet;   
 } 

 public static <T extends Object> Set<T> Array2Set2(T[] tArray) {   
     Set<T> tSet = new HashSet<T>();  
     Collections.addAll(tSet, tArray);    
     return tSet; 
 } 

java实现定时任务的三种方法

public class Task1 {  
    public static void main(String[] args) {  
   final long timeInterval = 1000;  
   Runnable runnable = new Runnable() {  
       public void run() {  
           while (true) {  
               System.out.println("Hello !!");
               try {  
                   Thread.sleep(timeInterval);  
               } catch (InterruptedException e) {  
                   e.printStackTrace();  
               }  
           }  
       }  
   };  
   Thread thread = new Thread(runnable);  
   thread.start();  
    }  
}  
public class Task2 {  
    public static void main(String[] args) {  
   TimerTask task = new TimerTask() {  
       @Override  
       public void run() {  
           System.out.println("Hello !!!");  
       }  
   };  
   Timer timer = new Timer();  
   long delay = 0;  
   long intevalPeriod = 1 * 1000; 
   timer.scheduleAtFixedRate(task, delay, intevalPeriod);  
    } 
}
public class Task3 {  
    public static void main(String[] args) {  
   Runnable runnable = new Runnable() {  
       public void run() { 
           System.out.println("Hello !!");  
       }  
   };  
   ScheduledExecutorService service = Executors  
           .newSingleThreadScheduledExecutor();  
   // 第二个参数为首次执行的延时时间，第三个参数为定时执行的间隔时间  
   service.scheduleAtFixedRate(runnable, 10, 1, TimeUnit.SECONDS);  
    }  
} 
//取消定时器：
timer.cancel();
//从当前时间立刻发起定时器
//timer.schedule(runTimes(args), new Date(), time);// 每隔一秒输出 

string 与 Array 互转

// string->array
     String seperateStr = "111,222,333,444,555,666,777";
//      String[] seperates = StringUtils.split(seperateStr, ",");
     String[] seperates = seperateStr.split(",");        
     for(String a :seperates){
         System.out.println(a);
     }       
// array->string
     String resultStr = StringUtils.join(seperates, ",");
     //System.out.println(Arrays.toString(seperates));
     //Arrays.asList(seperates)
     //Arrays.toString(new String[0])

JAVA中实现链式操作

//Persion.java：
public class Persion {
 private int id;
 private String name;   
 public  Persion() {    }
 public Persion setId(int id) { 
     this.id = id;
     return this;
 }
 public Persion setName(String name) {
     this.name = name;
     return this;
 }
 public Persion printId() {
     System.out.println(this.id);
     return this;
 }
 public Persion printName() {
     System.out.println(this.name);
     return this;
 }   
}

//Test.java：
public class Test {
 public static void main(String[] args) {
     Persion persion1 = new Persion();
     persion1.setId(3).setName("John");
     persion1.printId().printName();
 }
}

Java使用占位符拼接字符串

String stringFormat  = "error at position %s, encountered %s, expected %s ";
System.out.println(String.format(stringFormat, 123, 100, 456));  
String messageFormat ="error at  {0}, encountered {1}, expected {2}";
System.out.println(MessageFormat.format(messageFormat, new Date(), 100, 456));
String.format("%06d", 12) //000012

日期比较

 //   1. 第一种直接用字符串类的compareTo方法：
    String t1="20131011";
    String t2="20131030";
     int result = t1.compareTo(t2);
 //   2. 第二种是把这个日期字符串转换成long：
    SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");
    Date d1 = sdf.parse(t1);
    Date d2 = sdf.parse(t2);
    long result = d1.getTime()-d2.getTime();
 //   3. 第三种是把日期字符串转换成整形int：
    int int1 = Integer.parseInt(t1);
    int int2 = Integer.parseInt(t2);
    int result = int1-int2;
 //   注：result大于0，则t1>t2；
 //      result等于0，则t1=t2；
 //      result小于0，则t1<t2；

数据互通

 //同步开关
 Boolean  currentSign = true;
 int  poolSize = 10;
 ExecutorService fixedThreadPool = Executors.newFixedThreadPool(poolSize);
  if(currentSign){
        Thread t=new Thread(){
            private T param;
            private  String path;
            private Class  callback;
            private void init(T param,String path,Class  callback){
                this.param=param;
                this.path=path;
                this.callback=callback;
            };
            {
                init(param,path,callback);
            }
            public void run(){
                //保存信息操作
                try {
                    Client client = ClientBuilder.newClient();
                    Response response = client.target(url+path)
                            .register(JacksonFeature.class)
                            .request(MediaType.APPLICATION_JSON_TYPE)
                            .header("shd_yunzheng_api_key", "c5LjOzsxNDkwNTc5NTA5NDYy")
                            .post(Entity.entity(param, MediaType.APPLICATION_JSON_TYPE));
                            log.error("数据交互( url:{},parm:{})",(url+path),JSON.toJSONString(param));
                     response.readEntity(resMsg.class);
                }catch (Exception e) {
                    e.printStackTrace();
                }
            }
        };
        t.start();
    }
return null;

maven 使用本地jar

<dependency>
  <groupId>com.jun</groupId>
  <artifactId>abc</artifactId>
  <version>150</version>
  <scope>system</scope>
  <systemPath>${project.basedir}/src/main/resources/lib/abc.jar </systemPath>
</dependency>

自定义error

{
  "exception": "customized exception",
  "add-attribute": "add-attribute",
  "path": "customized path",
  "trace": "customized trace",
  "error": "customized error",
  "message": "customized message",
  "timestamp": 1498892609326,
  "status": 100
}

数组排序

 Collections.sort(infos, new Comparator<YzPhotoInfo>() {
 @Override
 public int compare(YzPhotoInfo o1, YzPhotoInfo o2) {
     int compareIntroduceId= o1.getIntroduceId().compareTo(o2.getIntroduceId());
     if(compareIntroduceId==0){
       return   o1.getPhoto().getName().compareTo(o2.getPhoto().getName());
     }
     return  compareIntroduceId;
 }
 });

java 常用方法

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