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package org.checkerframework.checker.optional.qual;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import org.checkerframework.framework.qual.PreconditionAnnotation;
/**
* Indicates a method precondition: the specified expressions of type Optional must be present
* (i.e., non-empty) when the annotated method is invoked.
*
* For example:
*
*
* import java.util.Optional;
*
* import org.checkerframework.checker.optional.qual.RequiresPresent;
* import org.checkerframework.checker.optional.qual.Present;
*
* class MyClass {
* Optional<String> optId1;
* Optional<String> optId2;
*
* @RequiresPresent({"optId1", "#1.optId1"})
* void method1(MyClass other) {
* optId1.get().length() // OK, this.optID1 is known to be present.
* optId2.get().length() // error, might throw NoSuchElementException.
*
* other.optId1.get().length() // OK, this.optID1 is known to be present.
* other.optId2.get().length() // error, might throw NoSuchElementException.
* }
*
* void method2() {
* MyClass other = new MyClass();
*
* optId1 = Optional.of("abc");
* other.optId1 = Optional.of("def")
* method1(other); // OK, satisfies method precondition.
*
* optId1 = Optional.empty();
* other.optId1 = Optional.empty("abc");
* method1(other); // error, does not satisfy this.optId1 method precondition.
*
* optId1 = Optional.empty("abc");
* other.optId1 = Optional.empty();
* method1(other); // error. does not satisfy other.optId1 method precondition.
* }
* }
*
*
* Do not use this annotation for formal parameters (instead, give them a {@code @Present} type).
* The {@code @RequiresNonNull} annotation is intended for non-parameter expressions, such as field
* accesses or method calls.
*
* @checker_framework.manual #optional-checker Optional Checker
*/
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD, ElementType.CONSTRUCTOR})
@PreconditionAnnotation(qualifier = Present.class)
public @interface RequiresPresent {
/**
* The Java expressions that that need to be {@link Present}.
*
* @return the Java expressions that need to be {@link Present}
* @checker_framework.manual #java-expressions-as-arguments Syntax of Java expressions
*/
String[] value();
/**
* A wrapper annotation that makes the {@link RequiresPresent} annotation repeatable.
*
* Programmers generally do not need to write this. It is created by Java when a programmer
* writes more than one {@link RequiresPresent} annotation at the same location.
*/
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD, ElementType.CONSTRUCTOR})
@PreconditionAnnotation(qualifier = Present.class)
public static @interface List {
/**
* Returns the repeatable annotations.
*
* @return the repeatable annotations
*/
RequiresPresent[] value();
}
}