SQL Developer Data Modeler

The font Arial has "proportional" character widths, that means that an "i" uses less space that a "m"

You could select a fond that is "nonpropotional" so that an "i" occupies the same space as a "m".

The most famous font of this type is  Courier

or you follow this advice:

Calculate the display width of a string in Java - Stack Overflow

bye

TPD

Cross posted and correctly answered at LineBreakMeasurer calculate text length is not match the length of line!

TPD-Opitz, the choice of Font has nothing to do with it.

I want to draw a line under a text. But the length that I calculate seems not equals to the length of the text. 

No! That is NOT true.

The 'length' that you calculate is EXACTLY equal to the length of the text.

int lineWidth = (int)layout.getBounds().getWidth();

That line widths is CORRECT.

But the line you DRAW is not the correct length because you are NOT specifying the parameters to 'drawLine' correctly:

g2d.drawLine(35, 150, lineWidth, 150);

You are using 'lineWidth' as the x coordinate of the second point. See the Java API for the method

Graphics (Java Platform SE 7 )

• drawLine

   public abstract void drawLine(int x1, int y1, int x2, int y2)
  Draws a line, using the current color, between the points (x1, y1) and (x2, y2) in this graphics context's coordinate system.
  
  

  Parameters:

  x1 - the first point's x coordinate.

  y1 - the first point's y coordinate.

  x2 - the second point's x coordinate.

  y2 - the second point's y coordinate.

See 'x2' the third parameter? That is "the second points's x coordinate. So it needs to be 'x1' plus the line width; you have to start at x1 and then go the line width to the right.