goto Opcode

Giriş
JVM iki tane goto Opcode tanımlıyor. Bunlar
- goto
- goto_w

goto Opcode
Açıklaması şöyle.

... goto is a reserved keyword in the Java language but is not actually used. And you probably also know that goto is a Java Virtual Machine (JVM) opcode.

goto_w Opcode
Açıklaması şöyle.

Whereas goto takes a 2-byte branch offset, goto_w takes a 4-byte branch offset. The spec states that

Bir başka açıklama şöyle.

The size of the method code can be as large as 64K.

The branch offset of the short goto is a signed 16-bit integer: from -32768 to 32767.

So, the short offset is not enough to make a jump from the beginning of 65K method to the end.

labeled Break

Örnek

Şöyle yaparız

public static void firstNumsToSum(List<Integer> nums1, List<Integer> nums2, int sum) {

  outer: for (Integer n1 : nums1) {
    inner: for (Integer n2 : nums2) {
      if (n1 + n2 == sum) {
        break outer;
      }
      System.out.println("n1=" + n1 + ", n2=" + n2);
    }
  System.out.println("here");
}

Örnek

Şöyle yaparız

public void updateDBRecord(User userToUpdate) {
   System.out.println("open DB connection");
   tryToPersist:
   try {
      User existingUser = db.read(userToUpdate.getUid());
      if (!needToUpdateRecord(existingUser, userToUpdate)) {
         break tryToPersist;
      }

      // recalculate + persist
      System.out.println("persist");
   } catch (Exception e) {
      System.out.println("Catastrophe");
   } finally {
      //close DB connection
      System.out.println("close DB connection");
   }
}