Why Java PrintStream have to Overload its print() functions?

Question

Here you are: http://developer.android.com/reference/java/io/PrintStream.html#print%28float%29

Just one function could serve all the purposes:

public void print (Object o) {
    if (o == null) {
        // print "null"
    } else {
        // print o.toString();
    }
}

More elaborations. For example, internal_print(String str) is a function that write to the print stream. Then the only one function needed would be:

public void print (Object o) {
    if (o == null) {
        internal_print( "null" );
    } else {
        internal_print( o.toString() );
    }
}

For other float, int, char, long, etc. overloadings, i can imagine they are just like:

public void print (float o) {
    if (o == null) {
        internal_print( "null" );
    } else {
        internal_print( o.toString() );
    }
}

public void print (int o) {
    if (o == null) {
        internal_print( "null" );
    } else {
        internal_print( o.toString() );
    }
}

public void print (char o) {
    if (o == null) {
        internal_print( "null" );
    } else {
        internal_print( o.toString() );
    }
}

public void print (long o) {
    if (o == null) {
        internal_print( "null" );
    } else {
        internal_print( o.toString() );
    }
}

...

Or even just calling the killer function print (Object o).

Could you please explain. Many thanks!!

Ooops good spot (Y) Thats my fault and typo. But after casted into `((Object) an_int)` in function parameter, it can check null and toString(). — midnite, Apr 02 '13 at 22:25

Joni · Accepted Answer · 2013-04-02T22:27:01.057

5

Historical reasons: the PrintStream class exists since Java 1.0, long before autoboxing was added (in 1.5).

Autoboxing is what would enable you to pass a primite type to print(Object o). Without it PrintStream had to implement an overload for each primitive type separately.

By the way, the implementations of print(..) for primitive types is more like:

public void print (int o) {
    print(String.valueOf(o));
}

... and the implementation of String.valueOf(..) basically delegates to methods in wrapper classes, such as Integer.toString(int) and Long.toString(long). You can read the source code at docjar.

edited Apr 02 '13 at 22:27

answered Apr 02 '13 at 22:19

Joni

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does "autoboxing" means casting `((Object) an_int)`? – midnite Apr 02 '13 at 22:23
1

Autoboxing means that primitive types such as `int` are automatically "boxed" in wrapper objects when you need to treat them like objects. http://docs.oracle.com/javase/tutorial/java/data/autoboxing.html – Joni Apr 02 '13 at 22:28

Why Java PrintStream have to Overload its print() functions?

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