What is the difference between initializing a Float with a String, or doing parseFloat?

Question

While coding a quick application, I noticed that there are two ways you could convert a String into a Float or an Integer.

Float f = new Float("0.0327f");
Float f = Float.parseFloat("0.0327f");

Similar methods exist for Integers. How are these two different?

Answer 1

Check their implementation (Oracle JDK 7)

public Float(String s) throws NumberFormatException {
    // REMIND: this is inefficient
    this(valueOf(s).floatValue());
}

where valueOf(String) is

public static Float valueOf(String s) throws NumberFormatException {
    return new Float(FloatingDecimal.readJavaFormatString(s).floatValue());
}

while parseFloat(String) is

public static float parseFloat(String s) throws NumberFormatException {
    return FloatingDecimal.readJavaFormatString(s).floatValue();
}

In the end, the two ways to generated the Float are equivalent. I say equivalent because in your example,

Float f = Float.parseFloat("0.0327f");

the float result of parseFloat will be boxed to a Float. The boxing process will basically wrap the previous call, ie. Float.valueOf(Float.parseFloat("0.0327f")) and the resulting Float's reference will be assigned to f.