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public static Set<String> strset = new HashSet<String>(); public static void permutation(String str) { Set<String> strSet = permutation("", str); for(String st:strSet) System.out.println(st); } private static Set<String> permutation(String prefix, String str) { int n = str.length(); if (n == 0) strset.add(prefix); else { for (int i = 0; i < n; i++) permutation(prefix + str.charAt(i), str.substring(0, i) + str.substring(i+1, n)); } return strset; } |
Covert String to byte array
We can use String class getBytes() method to encode the string into a sequence of bytes using the platform’s default charset. This method is overloaded and we can also pass Charset as argument. Here is a simple program showing how to convert String to byte array in java.
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public static void main(String[] args) { String str = "Faiz"; byte[] byteArr = name.getBytes(); System.out.println(Arrays.toString(byteArr)); } //output //[70, 97, 105, 122] |
Ignore case while find query using Mongodb.
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public List<Student> readByRhid(String emailId) { Query query = new Query(); Criteria criteria = Criteria.where(LabelConstant.STUDENT_DETAIL + "." + LabelConstant.EMAILID).regex("^"+emailId+"$", "i"); query.addCriteria(criteria); return mongoTemplate.find(query, Student.class); } |
Use This Criteria
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Criteria criteria = Criteria.where(LabelConstant.STUDENT_DETAIL + "." + LabelConstant.EMAILID).regex("^"+emailId+"$", "i"); |
How to add CORS with Spring?
1st Example For All Location
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@Configuration @EnableWebMvc public class WebConfig extends WebMvcConfigurerAdapter { @Override public void addCorsMappings(CorsRegistry registry) { registry.addMapping("/**"); } } |
2nd Example For Validate which location and which method to allow
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@Configuration @EnableWebMvc public class AppConfig extends WebMvcConfigurerAdapter { @Override public void addCorsMappings(CorsRegistry registry) { registry.addMapping("/**") .allowedOrigins("http://localhost:8585", "http://localhost:8787") .allowedMethods("POST", "GET", "PUT", "OPTIONS", "DELETE") .allowedHeaders("X-Auth-Token", "Content-Type") .exposedHeaders("custom-header1", "custom-header2") .allowCredentials(false) .maxAge(4800); } } |
How To Register Multiple Interceptor In Spring MVC?
Create Configuration Class extends with WebMvcConfigurerAdapter
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@Override public void addInterceptors(InterceptorRegistry registry) { // Register guest interceptor with single path pattern registry.addInterceptor(new GuestInterceptor()).addPathPatterns("/guest"); // Register admin interceptor with multiple path patterns registry.addInterceptor(new AdminInterceptor()) .addPathPatterns(new String[] { "/admin", "/admin/*" }); } |
Log4j Multiple Appender Simple Example in java
# Root logger option log4j.rootLogger=INFO, DEBUG, file,console # Console Appender log4j.appender.console=org.apache.log4j.ConsoleAppender log4j.appender.console.Append=true log4j.appender.console.layout=org.apache.log4j.PatternLayout log4j.appender.console.layout.ConversionPattern=%d{yyyy-MM-ddHH:mm:ss,SSS} %-5p [ %M ] ( %C ) %c{1}:%L – %m%n # File Appender log4j.appender.file=org.apache.log4j.FileAppender log4j.appender.file.DatePattern=’.’yyyy-MM-dd-HH-mm log4j.appender.file.Append=true log4j.appender.file.layout=org.apache.log4j.PatternLayout log4j.appender.file.layout.ConversionPattern=%d{yyyy-MM-ddHH:mm:ss,SSS} %-5p [ %M ] ( %C ) %c{1}:%L – %m%n log4j.appender.file.File=C:/log/SpringMain.log log4j.appender.file.MaxBackupIndex=10
Provide time zone to Spring @Scheduled or XML?
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//Annotation Based @Scheduled(cron = "0 10 19 * * FRI", zone = "CET") //XML Based <bean id="cronTrigger" class="org.springframework.scheduling.quartz.CronTriggerBean"> <property name="jobDetail" ref="schedulerJob" /> <property name="cronExpression" value="0 10 9 ? * * " /> <property name="timeZone" value="UTC"/> </bean> |
Preferred Java way to ping an HTTP URL for availability
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/** * * @param url * @return */ public Boolean validateURL(String url) { try { final URLConnection connection = new URL(url).openConnection(); connection.connect(); return true; } catch (final MalformedURLException e) { throw new IllegalStateException("Bad URL: " + url, e); } catch (final IOException e) { return false; } } |
Convert Date/Time for given Timezone – java
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public static Date convertDateToAnotherTimeZone(Date inputDate, String inputTimezoneCode, String targetTimezoneCode) { TimeZone fromTimezone = TimeZone.getTimeZone(inputTimezoneCode);// get Timezone object TimeZone toTimezone = TimeZone.getTimeZone(targetTimezoneCode); long fromOffset = fromTimezone.getOffset(inputDate.getTime());// get offset long toOffset = toTimezone.getOffset(inputDate.getTime()); // calculate offset difference and calculate the actual time long convertedTime = inputDate.getTime() - (fromOffset - toOffset); Date newDate = new Date(convertedTime); DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); df.format(newDate); return newDate; } |
Ignore DST when using Java Calendars
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private static Date offsetTimeZone(Date date, String fromTZ, String toTZ){ // Construct FROM and TO TimeZone instances TimeZone fromTimeZone = TimeZone.getTimeZone(fromTZ); TimeZone toTimeZone = TimeZone.getTimeZone(toTZ); // Get a Calendar instance using the default time zone and locale. Calendar calendar = Calendar.getInstance(); // Set the calendar's time with the given date calendar.setTimeZone(fromTimeZone); calendar.setTime(date); System.out.println("Input: " + calendar.getTime() + " in " + fromTimeZone.getDisplayName()); calendar.set(calendar.DST_OFFSET, 0); // this line to off DST // FROM TimeZone to UTC calendar.add(Calendar.MILLISECOND, fromTimeZone.getRawOffset() * -1); if (fromTimeZone.inDaylightTime(calendar.getTime())) { calendar.add(Calendar.MILLISECOND, calendar.getTimeZone().getDSTSavings() * -1); System.out.println("hrere"); } // UTC to TO TimeZone calendar.add(Calendar.MILLISECOND, toTimeZone.getRawOffset()); if (toTimeZone.inDaylightTime(calendar.getTime())) { calendar.add(Calendar.MILLISECOND, toTimeZone.getDSTSavings()); System.out.println("doing"); } return calendar.getTime(); } |