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The AWS SDK for Java with support for OSGi. The AWS SDK for Java provides Java APIs for building software on AWS' cost-effective, scalable, and reliable infrastructure products. The AWS Java SDK allows developers to code against APIs for all of Amazon's infrastructure web services (Amazon S3, Amazon EC2, Amazon SQS, Amazon Relational Database Service, Amazon AutoScaling, etc).

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/*
 * Copyright 2015-2016 Amazon Technologies, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 *
 *    http://aws.amazon.com/apache2.0
 *
 * This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES
 * OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and
 * limitations under the License.
 */
 package com.amazonaws.services.dynamodbv2.xspec;

import static com.amazonaws.services.dynamodbv2.xspec.ExpressionSpecBuilder._;

import com.amazonaws.annotation.Beta;

/**
 * Represents a condition for building condition expression.
 */
@Beta
public abstract class Condition extends UnitOfExpression {
    /**
     * Returns a new condition based on the negation of the current condition.
     */
    public final NegationCondition negate() {
        return new NegationCondition(this);
    }

    /**
     * Returns a new condition based on the conjunction of the current condition
     * and the given condition.
     * 
     * @param that given condition.
     */
    public AndCondition and(Condition that) {
        return new AndCondition(this, that.atomic() ? that : _(that));
    }

    /**
     * Returns a new condition based on the disjunction of the current condition
     * and the given condition. 
     * 
     * @param that given condition.
     */
    public OrCondition or(Condition that) {
        return new OrCondition(this, that.atomic() ? that : _(that));
    }

    /**
     * A condition is considered "atomic" if appending an additional AND condition
     * would not alter the evaluation order of the original condition;
     * false otherwise.  For example, "a == b AND c == d" is atomic, but
     * "a == b OR c == d" is not.
     */
    abstract boolean atomic();
    
    /**
     * Returns the precedence of this condition.
     * See http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.SpecifyingConditions.html#ConditionExpressionReference
     */
    abstract int precedence();
}