Detailed explanation and examples of the use of java statement blocks

java Statement Block

I still remember that when I first read C, C++ and Java programming books, statement blocks were introduced, but at that time I didn’t even understand what a statement block was. "Code Encyclopedia" also talks about organizing statements with similar functions together to form statement blocks, and then separating them from other statement blocks with blank lines. But this is only a statement block in human understanding, not a statement block in the true programming language sense.

From my understanding, the program definition should be a set of related statements with the same variable scope. It seems that it should be enclosed in {}, such as a control structure. logic in. I think the most critical point is variable scope, that is to say, if the same local variable can be used, it is a statement block in the program sense. Let’s look at an example:

@Override 
public boolean onOptionsItemSelected(MenuItem item) { 
 switch (item.getItemId()) { 
 case MENU_GOTO_FILEANT: 
 Intent i = new Intent(); 
 i.setClass(this, FileAntActivity.class); 
 startActivity(i); 
 break; 
 case MENU_TEST_LINEARLAYOUT: 
 i.setClass(this, LinearLayoutTest.class); 
 startActivity(i); 
 break; 
 default: 
 break; 
 } 
 return true; 
}

For the second case statement, you can still use the variables defined in the previous case, so the entire switch() {} is a statement block.

But if you add a statement block mark to each case statement, it will be different:

@Override
public boolean onOptionsItemSelected(MenuItem item) {
 switch (item.getItemId()) {
 case MENU_GOTO_FILEANT: {
 Intent i = new Intent();
 i.setClass(this, FileAntActivity.class);
 startActivity(i);
 break;
 }
 case MENU_TEST_LINEARLAYOUT: {
 Intent i = new Intent();
 i.setClass(this, LinearLayoutTest.class);
 startActivity(i);
 break;
 }
 default:
 break;
 }
 return true;
}

Added { } separates the two case statements to form two statement blocks. They have their own variable scopes and do not affect each other. It does not matter even if they have the same name or are defined again.

The purpose of explaining these is to use {} as much as possible to form a real statement block. The biggest advantage is that it can form a variable scope and avoid the scope of the variable being too large. This improves readability and reduces the possibility of errors.

Thank you for reading, I hope it can help you, thank you for your support of this site!

For more detailed explanations and examples of the use of java statement blocks, please pay attention to the PHP Chinese website!