Control Flow

block, also known as compound statement.

总体跟 C 保持一致，但是：

• nested scope can’t redefine an exsist name

”for each” Loop

switch case

A case label can be

• A constant expression of type char, byte, short, or int
• An enumerated constant
• Starting with Java 7, a string literal

labeled break

Scanner in = new Scanner(System.in); 
int n; 
read_data:
while (. . .) {  // this loop statement is *tagged with the label*
	. . .
	for (. . .) {  // this inner loop *is not labeled* 
		System.out.print("Enter a number >= 0: "); 
		n = in.nextInt(); 
		if (n < 0)   // should never happen—can't go on 
		break read_data; // break out of read_data loop . . .
	}
}  // this statement is executed immediately after the labeled break 
 
if (n < 0) {  // check for bad situation 
	// deal with bad situation 
} else {
	// carry out normal processing 
}

Notice that the label must precede the outermost loop out of which you want to break. (估计就是在labeled break所在的loop前做标记)

也就是说这并不是一个 goto，label仅仅只是对一块block做标记，当运行到labeled break的时候，就会走到 the end of the labeled block

goto imitation

label:
{
	/* to do something */
	if (condition) break label;  // exits block . . .
	/* to do something */
}
// jumps here when the break statement executes

Note, however, that you can only jump out of a block, never into a block.