Difference between parseInt and valueOf in java?

Question

What's the difference between these two methods? They appear to do exactly the same thing to me (also goes for parseFloat(), parseDouble(), parseLong() etc, how are they different from Long.valueOf(string) ?

Edit: Also, which of these is preferable and used more often by convention?

Answer 1

From this forum:

parseInt() returns primitive integer type (int), whereby valueOf returns java.lang.Integer, which is the object representative of the integer. There are circumstances where you might want an Integer object, instead of primitive type.

Of course, another obvious difference is that intValue is an instance method whereby parseInt is a static method.

Answer 2

valueOf(s)

is similar to

new Integer(Integer.parseInt(s))

The difference is valueOf() returns an Integer, and parseInt() returns an int (a primitive type). Also note that valueOf() can return a cached Integer instance, which can cause confusing results where the result of == tests seem intermittently correct. Before autoboxing there could be a difference in convenience, after java 1.5 it doesn't really matter.

Answer 3

The parse* variations return primitive types and the valueOf versions return Objects. I believe the valueOf versions will also use an internal reference pool to return the SAME object for a given value, not just another instance with the same internal value.

Answer 4

Well, the API for Integer.valueOf(String) does indeed say that the String is interpreted exactly as if it were given to Integer.parseInt(String). However, valueOf(String) returns a new Integer() object whereas parseInt(String) returns a primitive int.

If you want to enjoy the potential caching benefits of Integer.valueOf(int), you could also use this eyesore:

Integer k = Integer.valueOf(Integer.parseInt("123"))

Now, if what you want is the object and not the primitive, then using valueOf(String) may be more attractive than making a new object out of parseInt(String) because the former is consistently present across Integer, Long, Double, etc.

Answer 5

Integer.parseInt can just return int as native type.

Integer.valueOf may actually need to allocate an Integer object, unless that integer happens to be one of the preallocated ones. This costs more.

If you need just native type, use parseInt. If you need an object, use valueOf.

Also, because of this potential allocation, autoboxing isn't actually good thing in every way. It can slow down things.

Answer 6

1. In case of ValueOf -> it is creating an Integer object. not a primitive type and not a static method.
2. In case of ParseInt.ParseFloat -> it return respective primitive type. and is a static method.

We should use any one depending upon our need. In case of ValueOf as it is instantiating an object. it will consume more resources if we only need value of some text then we should use parseInt,parseFloat etc.

Answer 7

Try this

Integer a = Integer.valueOf("10");
Integer b = Integer.valueOf("10");
if (a.equals(b)) {
System.out.println("Equals");
} else {
System.out.println("Not Equals");
}
if (a == b) {
System.out.println("a == b");
} else {
System.out.println("a != b");
}


If you run this example; the result is

Equals
a != b

So Integer.valueOf() does not return the same object.

Even tools like PMD, findBugs recommend using .valueOf()