public class Test {
    private Test() {}
    public static void main(String... args) {
int i = 1;
String s = ""+i;
    }
}

$ /usr/java/jdk1.6.0/bin/javac -J-showversion Test.java
java version "1.6.0-ea"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.6.0-ea-b52)
Java HotSpot(TM) Client VM (build 1.6.0-ea-b52, mixed mode, sharing)
 
$ javap -c Test
Compiled from "Test.java"
public class Test extends java.lang.Object{
public static void main(java.lang.String[]);
  Code:
   0: iconst_1
   1: istore_1
   2: new #2; //class java/lang/StringBuilder
   5: dup
   6: invokespecial #3; //Method java/lang/StringBuilder."<init>":()V
   9: ldc #4; //String
   11: invokevirtual #5; //Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
   14: iload_1
   15: invokevirtual #6; //Method java/lang/StringBuilder.append:(I)Ljava/lang/StringBuilder;
   18: invokevirtual #7; //Method java/lang/StringBuilder.toString:()Ljava/lang/String;
   21: astore_2
   22: return
 
}
 
The compiler should be able to generate this code:

  Code:
   0: iconst_1
   1: istore_1
   2: iload_1
   3: invokestatic #2; //Method java/lang/String.valueOf:(I)Ljava/lang/String;
   6: astore_2
   7: return