OPEN GL model not fully displayed?

Question

Java

Hello. I display the obj model on the screen, but for some reason it is not displayed completely, so-called "holes" appear on the figure. What is the problem?
Below is the render class:

public SceneRenderer(ObjModel objModel, List<ObjTexture> objTextureList) throws Exception {
        glEnable(GL_DEPTH_TEST);
        glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
        glPointSize(10);
        String fragmentSource = IOUtils.toString(getClass().getResourceAsStream("shader.frag"));
        String vertexSource = IOUtils.toString(getClass().getResourceAsStream("shader.vert"));
        shaderProgram = Util.createShaderProgram(vertexSource, fragmentSource);
        for (ObjTexture objTexture : objTextureList) {
            int vaoTriangles = glGenVertexArrays();
            List<MultiIndex> multiIndices = objModel.getFaces(objTexture.getNameTexture());
            List<Polygon> polygons = objModel.getPolygons(objTexture.getNameTexture());
            vbao.add(new ArrayIdTriangle(vaoTriangles, multiIndices.size(), objTexture));
            glBindVertexArray(vaoTriangles);
            int vertexBuffer = glGenBuffers();
            glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
            glBufferData(GL_ARRAY_BUFFER, Geometry.getVertexCoord(objModel.getVertices(), multiIndices).rewind(), GL_STATIC_DRAW);
            glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
            glVertexAttribPointer(0, 3, GL_FLOAT, false, 0, 0);
            int normalBuffer = glGenBuffers();
            glBindBuffer(GL_ARRAY_BUFFER, normalBuffer);
            glBufferData(GL_ARRAY_BUFFER, Geometry.getNormals(polygons, multiIndices).rewind(), GL_STATIC_DRAW);
            glBindBuffer(GL_ARRAY_BUFFER, normalBuffer);
            glVertexAttribPointer(1, 3, GL_FLOAT, false, 0, 0);
            int textureBuffer = glGenBuffers();
            glBindBuffer(GL_ARRAY_BUFFER, textureBuffer);
            glBufferData(GL_ARRAY_BUFFER, Geometry.getTexture(objModel.getTexCoords(), multiIndices).rewind(), GL_STATIC_DRAW);
            glBindBuffer(GL_ARRAY_BUFFER, textureBuffer);
            glVertexAttribPointer(textureLocation, 2, GL_FLOAT, false, 0, 0);
        }
        glBindBuffer(GL_ARRAY_BUFFER, 0);
        glBindVertexArray(0);
    }
    void render() throws Exception {
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // clear the framebuffer
        FloatBuffer vMatrix = BufferUtils.createFloatBuffer(16);
        new Matrix4f()
                .lookAt(cameraPosition.x, cameraPosition.y, cameraPosition.z,
                        0.0f, 0.0f, 0.0f,
                        0.0f, 1.0f, 0.0f).get(vMatrix);

        FloatBuffer mMatrix = BufferUtils.createFloatBuffer(16);
        new Matrix4f().translate(modelPosition)
                .rotateX(modelRotation.x)
                .rotateY(modelRotation.y)
                .rotateZ(modelRotation.z)
                .scale(modelScale)
                .get(mMatrix);
        glUseProgram(shaderProgram);
        glUniformMatrix4fv(glGetUniformLocation(shaderProgram, "P"), false, pMatrix);
        glUniformMatrix4fv(glGetUniformLocation(shaderProgram, "V"), false, vMatrix);
        glUniformMatrix4fv(glGetUniformLocation(shaderProgram, "M"), false, mMatrix);
        glUniform3f(glGetUniformLocation(shaderProgram, "light_worldspace"), lightPosition.x, lightPosition.y, lightPosition.z);
        for (ArrayIdTriangle aVbao : vbao) {
            if (aVbao.getTexture() == null) {
                aVbao.setTexture(new Texture(ConstPath.FILE_TEXTURE.filePath + aVbao.getObjTexture().getTexturePath()));
            }
            glActiveTexture(GL_TEXTURE0);
            glBindTexture(GL_TEXTURE_2D, aVbao.getTexture().getId());
            glBindVertexArray(aVbao.getId());
            glEnableVertexAttribArray(vertexLocation);
            glEnableVertexAttribArray(textureLocation);
            glEnableVertexAttribArray(normalLocation);
            glDrawArrays(GL_TRIANGLES, 0, aVbao.getSize());
        }
    }

I read the model from the obj file and divide it into groups of triangles according to the same textures.
ArrayIdTriangle- contains the texture, the path to the texture and the name of the texture in the obj file
multiIndices- contains the indexes of the i-th group of triangles with a common texture.

Geometry.getVertexCoord(objModel.getVertices(), multiIndices)

- finds all vertices for which the texture is used

Answer 1

Alas, not a programmer (but since they called) perhaps the model itself has "inverted" normals, looking from the camera and discarded during rendering.