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diff --git a/src/main/java/org/apache/commons/math3/ode/FirstOrderIntegrator.java b/src/main/java/org/apache/commons/math3/ode/FirstOrderIntegrator.java
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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License 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 org.apache.commons.math3.ode;
+
+import org.apache.commons.math3.exception.DimensionMismatchException;
+import org.apache.commons.math3.exception.MaxCountExceededException;
+import org.apache.commons.math3.exception.NoBracketingException;
+import org.apache.commons.math3.exception.NumberIsTooSmallException;
+
+/**
+ * This interface represents a first order integrator for differential equations.
+ *
+ * <p>The classes which are devoted to solve first order differential equations should implement
+ * this interface. The problems which can be handled should implement the {@link
+ * FirstOrderDifferentialEquations} interface.
+ *
+ * @see FirstOrderDifferentialEquations
+ * @see org.apache.commons.math3.ode.sampling.StepHandler
+ * @see org.apache.commons.math3.ode.events.EventHandler
+ * @since 1.2
+ */
+public interface FirstOrderIntegrator extends ODEIntegrator {
+
+    /**
+     * Integrate the differential equations up to the given time.
+     *
+     * <p>This method solves an Initial Value Problem (IVP).
+     *
+     * <p>Since this method stores some internal state variables made available in its public
+     * interface during integration ({@link #getCurrentSignedStepsize()}), it is <em>not</em>
+     * thread-safe.
+     *
+     * @param equations differential equations to integrate
+     * @param t0 initial time
+     * @param y0 initial value of the state vector at t0
+     * @param t target time for the integration (can be set to a value smaller than <code>t0</code>
+     *     for backward integration)
+     * @param y placeholder where to put the state vector at each successful step (and hence at the
+     *     end of integration), can be the same object as y0
+     * @return stop time, will be the same as target time if integration reached its target, but may
+     *     be different if some {@link org.apache.commons.math3.ode.events.EventHandler} stops it at
+     *     some point.
+     * @exception DimensionMismatchException if arrays dimension do not match equations settings
+     * @exception NumberIsTooSmallException if integration step is too small
+     * @exception MaxCountExceededException if the number of functions evaluations is exceeded
+     * @exception NoBracketingException if the location of an event cannot be bracketed
+     */
+    double integrate(
+            FirstOrderDifferentialEquations equations, double t0, double[] y0, double t, double[] y)
+            throws DimensionMismatchException,
+                    NumberIsTooSmallException,
+                    MaxCountExceededException,
+                    NoBracketingException;
+}