Why Float.valueOf("2.7") > 2.7 gives me true?

The literal 2.7 is a double - i.e. the closest double value to 2.7.

Float.valueOf("2.7") - or 2.7f, equivalently, is the closest float value to 2.7. Neither of them will be exactly 2.7 - and in this case, they're both slightly greater than 2.7. The actual values are:

float:  2.7000000476837158203125
double: 2.70000000000000017763568394002504646778106689453125

As you can see, the float value really is greater than the double value.

In cases where the closest value is lower than the "ideal" one, you'll see the reverse effect, where the float value will be smaller than the double value, because the double value will be closer to the "ideal" one. You'll see that with 2.8, for example, where the values are:

float:  2.7999999523162841796875
double: 2.79999999999999982236431605997495353221893310546875

If you use Double.parseDouble instead of Float.parseFloat - or alternatively, if you make the comparisons work against the float literals, you should get the expected result:

System.out.println(Float.valueOf("2.7") > 2.7f);
System.out.println(Double.valueOf("2.7") > 2.7);