$ cat Foo.java class Foo { String foo(String[] ss) { String buf = ""; for (int i = 0; i < ss.length; ++i) { buf += ss[i]; } return buf; } } $ javac Foo.java $ javap -c Foo Compiled from "Foo.java" class Foo extends java.lang.Object{ Foo(); Code: 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V 4: return java.lang.String foo(java.lang.String[]); Code: 0: ldc #2; //String 2: astore_2 3: iconst_0 4: istore_3 5: iload_3 6: aload_1 7: arraylength 8: if_icmpge 38 11: new #3; //class java/lang/StringBuilder 14: dup 15: invokespecial #4; //Method java/lang/StringBuilder."<init>":()V 18: aload_2 19: invokevirtual #5; //Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder; 22: aload_1 23: iload_3 24: aaload 25: invokevirtual #5; //Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder; 28: invokevirtual #6; //Method java/lang/StringBuilder.toString:()Ljava/lang/String; 31: astore_2 32: iinc 3, 1 35: goto 5 38: aload_2 39: areturn }