Java does not support goto

Reading time: 20 minutes | Coding time: 5 minutes

In Java, goto is a reserved word but it has not implemented in Java. Hence, we do not have a same goto keyword/ feature as in other languages like C and C++.

Key points for Java:

• Java does not support goto but it is a reserved word
• Java does support labels
• Java does support continue and break which use label

Why goto is not supported?

In software engineering practices, it is strongly advised not to use goto as it increases the code complexity greatly.

In legacy code, it has been seen that the use of goto has made it difficult for new developers for developing new features. For this, Java developers skipped added goto functionality but added it is a reserved keyword so it is possible to added such a feature later if required.

So, currently, it is not possible to use goto but one can develop a external library to implement this feature of goto using another statement such as goto2. This is possible as Java does support limited program flow control using:

• labels
• continue
• break

and the compiler infrastructure supports explicit program flow control.

Currently, there is not such production level library.

If we try to use goto in Java, we will get a compile time error like:

class OpenGenus 
{
	public static void main (String[] args) 
	{
		loop: System.out.println("1");
		if (true) continue loop;
		System.out.println("2");
	}
}

Compile time error:

prog.java:6: error: illegal start of expression
		if (true) goto loop;
		          ^
prog.java:6: error: not a statement
		if (true) goto loop;
		               ^
2 errors

As goto is a reserved word, one cannot use it as an identifier. In case, we try to do so, we will get a compile time error like:

class OpenGenus 
{
	public static void main (String[] args) 
	{
		int goto = 2;
	}
}

Compile time error:

prog.java:5: error: not a statement
		int goto = 2;
		^
prog.java:5: error: ';' expected
		int goto = 2;
		   ^
2 errors

Implementing similar feature

We can use break statement to skip some code statements by enclosing code statements in a labeled code block.

Example:

class OpenGenus 
{
	public static void main (String[] args) 
	{
		loop: {
		    System.out.println("1");
		    if (true) break loop;
		    System.out.println("2");
		}
		System.out.println("3");
	}
}

Output:

1
3

We can use a continue statement in a limited way to deal with loops:

class OpenGenus 
{
	public static void main (String[] args) 
	{
		loop: 
		for(int i=0; i< 3; i++)
		{
		    if (i==1) 
		        continue loop;
		    System.out.println(i);
		}
		System.out.println("--");
	}
}

Output:

0
2
--