public void copy(Matrix4f matrix) {
        if (null == matrix) {
            loadIdentity();
        } else {
            m00 = matrix.m00;
            m01 = matrix.m01;
            m02 = matrix.m02;
            m03 = matrix.m03;
            m10 = matrix.m10;
            m11 = matrix.m11;
            m12 = matrix.m12;
            m13 = matrix.m13;
            m20 = matrix.m20;
            m21 = matrix.m21;
            m22 = matrix.m22;
            m23 = matrix.m23;
            m30 = matrix.m30;
            m31 = matrix.m31;
            m32 = matrix.m32;
            m33 = matrix.m33;
        }
    }
Copy all elements of the specified matrix to this matrix. If null is
specified, load identity (diagonals = 1, other elements = 0).

@param matrix the source matrix (may be null, unaffected)
jme3-core/src/main/java/com/jme3/math/Matrix4f.java