Demonstrate implicit StringBuilder

gistfile1.txt

$ cat foo.java
public class foo {
    private foo() {}
    public static String method(int x, Long y) {
        return "x: " + x + " y: " + y.longValue();
    }
}

$ javac foo.java

$ javap -c foo 
Compiled from "foo.java"
public class foo extends java.lang.Object{
public static java.lang.String method(int, java.lang.Long);
  Code:
   0:   new     #2; //class java/lang/StringBuilder
   3:   dup
   4:   invokespecial   #3; //Method java/lang/StringBuilder."<init>":()V
   7:   ldc     #4; //String x: 
   9:   invokevirtual   #5; //Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
   12:  iload_0
   13:  invokevirtual   #6; //Method java/lang/StringBuilder.append:(I)Ljava/lang/StringBuilder;
   16:  ldc     #7; //String  y: 
   18:  invokevirtual   #5; //Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
   21:  aload_1
   22:  invokevirtual   #8; //Method java/lang/Long.longValue:()J
   25:  invokevirtual   #9; //Method java/lang/StringBuilder.append:(J)Ljava/lang/StringBuilder;
   28:  invokevirtual   #10; //Method java/lang/StringBuilder.toString:()Ljava/lang/String;
   31:  areturn

}