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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.checker.index.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.JavaExpression;
import org.checkerframework.framework.qual.SubtypeOf;

/**
 * An annotation indicating the relationship between values with a byte, short, char, int, or long
 * type.
 *
 * If an expression's type has this annotation, then at run time, the expression evaluates to a
 * value that is less than the value of the expression in the annotation.
 *
 * 
Subtyping:
 *
 * 

 *   {@code @LessThan({"a", "b"}) <: @LessThan({"a"})}
 *   
{@code @LessThan({"a", "b"})} is not related to {@code @LessThan({"a", "c"})}.
 * 
 *
 * @checker_framework.manual #index-inequalities Index Checker Inequalities
 */
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE_PARAMETER, ElementType.TYPE_USE})
@SubtypeOf({LessThanUnknown.class})
// TODO: I chose to implement less than rather than greater than because in most of the case studies
// false positives, the bigger value is final or effectively final, so it can appear in a dependent
// annotation without causing soundness issues.
public @interface LessThan {
  /**
   * The annotated expression's value is less than this expression.
   *
   * The expressions in {@code value} may be addition/subtraction of any number of Java
   * expressions. For example, {@code @LessThan(value = "x + y + 2"}}.
   *
   * The expression in {@code value} must be final or constant or the addition/subtract of final
   * or constant expressions.
   */
  @JavaExpression
  String[] value();
}