Is there any java class to get Date from cron expression

I need to find out the first occurrence of Date and time represented by given cro开发者_运维问答n expression. Is there any java class, utility code which can help in getting data object from given cron expression ?

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You can also leverage on spring's http://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/scheduling/support/CronSequenceGenerator.html for this

CronSequenceGenerator generator = new CronSequenceGenerator(cronExpression);
Date nextRunDate= generator.next(new Date());

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You can check org.quartz.CronExpression It has a method named getNextValidTimeAfter which you can use.

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If you're using Spring you could use:

CronTrigger trigger = new CronTrigger(cron);
TriggerContext context = new TriggerContext() {

public Date lastScheduledExecutionTime() {
    return null;
}

public Date lastActualExecutionTime() {
    return null;
}

public Date lastCompletionTime() {
    return null;
}
};
return trigger.nextExecutionTime(context);

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Here's an alternative similar to Quartz's CronExpression but without having to add a fully fledged scheduler to your project: cron-utils

You can get the date you need with the following:

//Get date for next execution
DateTime now = DateTime.now();
CronDefinition cronDefinition = CronDefinitionBuilder.instanceDefinitionFor(QUARTZ);
CronParser parser = new CronParser(cronDefinition);
ExecutionTime executionTime = ExecutionTime.forCron(parser.parse("* * * * * * *"));
DateTime nextExecution = executionTime.nextExecution(now));

According to the official description, cron-utils is:

A Java library to parse, validate, migrate crons as well as get human readable descriptions for them. The project follows the Semantic Versioning Convention and uses Apache 2.0 license.

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It looks like you could use either of these:

• j-cron-expression
• Quartz CronTrigger class