org.checkerframework.checker.nullness.qual.RequiresNonNull Maven / Gradle / Ivy
package org.checkerframework.checker.nullness.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;
// TODO: In a fix for https://tinyurl.com/cfissue/1917, add the text: Every prefix expression must
// also be non-null; for example, {@code @RequiresNonNull(expression="a.b.c")} implies that both
// {@code a.b} and {@code a.b.c} must be non-null.
/**
* Indicates a method precondition: the method expects the specified expressions to be non-null when
* the annotated method is invoked.
*
* For example:
*
*
*
* class MyClass {
* @Nullable Object field1;
* @Nullable Object field2;
*
* @RequiresNonNull({"field1", "#1.field1"})
* void method1(@NonNull MyClass other) {
* field1.toString(); // OK, this.field1 is known to be non-null
* field2.toString(); // error, might throw NullPointerException
* other.field1.toString(); // OK, other.field1 is known to be non-null
* other.field2.toString(); // error, might throw NullPointerException
* }
*
* void method2() {
* MyClass other = new MyClass();
*
* field1 = new Object();
* other.field1 = new Object();
* method1(other); // OK, satisfies method precondition
*
* field1 = null;
* other.field1 = new Object();
* method1(other); // error, does not satisfy this.field1 method precondition
*
* field1 = new Object();
* other.field1 = null;
* method1(other); // error, does not satisfy other.field1 method precondition
* }
* }
*
*
* Do not use this annotation for formal parameters (instead, give them a {@code @NonNull} type,
* which is the default and need not be written). The {@code @RequiresNonNull} annotation is
* intended for other expressions, such as field accesses or method calls.
*
* @checker_framework.manual #nullness-checker Nullness Checker
*/
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD, ElementType.CONSTRUCTOR})
@PreconditionAnnotation(qualifier = NonNull.class)
public @interface RequiresNonNull {
/**
* The Java expressions that need to be {@link
* org.checkerframework.checker.nullness.qual.NonNull}.
*
* @checker_framework.manual #java-expressions-as-arguments Syntax of Java expressions
*/
String[] value();
}