Assembly Language for Beginners

4.1. JAVA

The string the user entered is reloaded at offset 30 and concatenated with the “Hello, ” string using the
StringBuilderclass.

The constructed string is then printed usingprintlnat offset 37.

Second example

Another example:

public class strings
{
public static char test (String a)
{
return a.charAt(3);
};

public static String concat (String a, String b)
{
return a+b;
}
}

public static char test(java.lang.String);

flags: ACC_PUBLIC, ACC_STATIC

Code:

stack=2, locals=1, args_size=1

0: aload_0

1: iconst_3

2: invokevirtual #2 // Method java/lang/String.charAt:(I)C

5: ireturn

The string concatenation is performed usingStringBuilder:

public static java.lang.String concat(java.lang.String, java.lang.String);

flags: ACC_PUBLIC, ACC_STATIC

Code:

stack=2, locals=2, args_size=2

0: new #3 // class java/lang/StringBuilder

3: dup

4: invokespecial #4 // Method java/lang/StringBuilder."<init>":()V

7: aload_0

8: invokevirtual #5 // Method java/lang/StringBuilder.append:(Ljava/lang/String⤦

Ç;)Ljava/lang/StringBuilder;

11: aload_1

12: invokevirtual #5 // Method java/lang/StringBuilder.append:(Ljava/lang/String⤦

Ç;)Ljava/lang/StringBuilder;

15: invokevirtual #6 // Method java/lang/StringBuilder.toString:()Ljava/lang/⤦

ÇString;

18: areturn

Another example:

public static void main(String[] args)

{

String s="Hello!";

int n=123;

System.out.println("s=" + s + " n=" + n);

}

And again, the strings are constructed using theStringBuilderclass and itsappendmethod, then the
constructed string is passed toprintln:

public static void main(java.lang.String[]);

flags: ACC_PUBLIC, ACC_STATIC

Code:

stack=3, locals=3, args_size=1

0: ldc #2 // String Hello!

2: astore_1