[wpimath] Move Java classes to edu.wpi.first.math (#3316)

wpimath/src/main/java/edu/wpi/first/math/MatBuilder.java

@@ -0,0 +1,53 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+package edu.wpi.first.math;
+
+import java.util.Objects;
+import org.ejml.simple.SimpleMatrix;
+
+/**
+ * A class for constructing arbitrary RxC matrices.
+ *
+ * @param <R> The number of rows of the desired matrix.
+ * @param <C> The number of columns of the desired matrix.
+ */
+public class MatBuilder<R extends Num, C extends Num> {
+  final Nat<R> m_rows;
+  final Nat<C> m_cols;
+
+  /**
+   * Fills the matrix with the given data, encoded in row major form. (The matrix is filled row by
+   * row, left to right with the given data).
+   *
+   * @param data The data to fill the matrix with.
+   * @return The constructed matrix.
+   */
+  @SuppressWarnings("LineLength")
+  public final Matrix<R, C> fill(double... data) {
+    if (Objects.requireNonNull(data).length != this.m_rows.getNum() * this.m_cols.getNum()) {
+      throw new IllegalArgumentException(
+          "Invalid matrix data provided. Wanted "
+              + this.m_rows.getNum()
+              + " x "
+              + this.m_cols.getNum()
+              + " matrix, but got "
+              + data.length
+              + " elements");
+    } else {
+      return new Matrix<>(new SimpleMatrix(this.m_rows.getNum(), this.m_cols.getNum(), true, data));
+    }
+  }
+
+  /**
+   * Creates a new {@link MatBuilder} with the given dimensions.
+   *
+   * @param rows The number of rows of the matrix.
+   * @param cols The number of columns of the matrix.
+   */
+  public MatBuilder(Nat<R> rows, Nat<C> cols) {
+    this.m_rows = Objects.requireNonNull(rows);
+    this.m_cols = Objects.requireNonNull(cols);
+  }
+}