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The Checker Framework enhances Java's type system to make it more powerful and useful. This lets software developers detect and prevent errors in their Java programs. The Checker Framework includes compiler plug-ins ("checkers") that find bugs or verify their absence. It also permits you to write your own compiler plug-ins.

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package org.checkerframework.dataflow.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;

/**
 * {@code TerminatesExecution} is a method annotation that indicates that a method terminates the
 * execution of the program. This can be used to annotate methods such as {@code System.exit()}, or
 * methods that unconditionally throw an exception.
 *
 * The annotation enables flow-sensitive type refinement to be more precise. For example, after
 *
 * 
 * if (x == null) {
 *   System.err.println("Bad value supplied");
 *   System.exit(1);
 * }
 * 
 *
 * the Nullness Checker can determine that {@code x} is non-null.
 *
 * The annotation is a trusted annotation, meaning that it is not checked whether the
 * annotated method really does terminate the program.
 *
 * 
This annotation is inherited by subtypes, just as if it were meta-annotated with
 * {@code @InheritedAnnotation}.
 *
 * 
The Checker Framework recognizes this annotation, but the Java compiler {@code javac} does
 * not. After calling a method annotated with {@code TerminatesExecution}, to prevent a {@code
 * javac} diagnostic, you generally need to insert a {@code throw} statement (which you know will
 * never execute):
 *
 * 
 * ...
 * myTerminatingMethod();
 * throw new Error("unreachable");
 * 
 *
 * @checker_framework.manual #type-refinement Automatic type refinement (flow-sensitive type
 *     qualifier inference)
 */
// @InheritedAnnotation cannot be written here, because "dataflow" project cannot depend on
// "framework" project.
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD, ElementType.CONSTRUCTOR})
public @interface TerminatesExecution {}