The Java Tutorials have been written for JDK 8. Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available.
See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases.
See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.
break
StatementThe break
statement has two forms: labeled and unlabeled. You saw the unlabeled form in the previous discussion of the switch
statement. You can also use an unlabeled break
to terminate a for
, while
, or do-while
loop, as shown in the following
BreakDemo
program:
class BreakDemo { public static void main(String[] args) { int[] arrayOfInts = { 32, 87, 3, 589, 12, 1076, 2000, 8, 622, 127 }; int searchfor = 12; int i; boolean foundIt = false; for (i = 0; i < arrayOfInts.length; i++) { if (arrayOfInts[i] == searchfor) { foundIt = true; break; } } if (foundIt) { System.out.println("Found " + searchfor + " at index " + i); } else { System.out.println(searchfor + " not in the array"); } } }
This program searches for the number 12 in an array. The break
statement, shown in boldface, terminates the for
loop when that value is found. Control flow then transfers to the statement after the for
loop. This program's output is:
Found 12 at index 4
An unlabeled break
statement terminates the innermost switch
, for
, while
, or do-while
statement, but a labeled break
terminates an outer statement. The following program,
BreakWithLabelDemo
, is similar to the previous program, but uses nested for
loops to search for a value in a two-dimensional array. When the value is found, a labeled break
terminates the outer for
loop (labeled "search"):
class BreakWithLabelDemo { public static void main(String[] args) { int[][] arrayOfInts = { { 32, 87, 3, 589 }, { 12, 1076, 2000, 8 }, { 622, 127, 77, 955 } }; int searchfor = 12; int i; int j = 0; boolean foundIt = false; search: for (i = 0; i < arrayOfInts.length; i++) { for (j = 0; j < arrayOfInts[i].length; j++) { if (arrayOfInts[i][j] == searchfor) { foundIt = true; break search; } } } if (foundIt) { System.out.println("Found " + searchfor + " at " + i + ", " + j); } else { System.out.println(searchfor + " not in the array"); } } }
This is the output of the program.
Found 12 at 1, 0
The break
statement terminates the labeled statement; it does not transfer the flow of control to the label. Control flow is transferred to the statement immediately following the labeled (terminated) statement.
continue
StatementThe continue
statement skips the current iteration of a for
, while
, or do-while
loop. The unlabeled form skips to the end of the innermost loop's body and evaluates the boolean
expression that controls the loop. The following program,
ContinueDemo
, steps through a String
, counting the occurrences of the letter "p". If the current character is not a p, the continue
statement skips the rest of the loop and proceeds to the next character. If it is a "p", the program increments the letter count.
class ContinueDemo { public static void main(String[] args) { String searchMe = "peter piper picked a " + "peck of pickled peppers"; int max = searchMe.length(); int numPs = 0; for (int i = 0; i < max; i++) { // interested only in p's if (searchMe.charAt(i) != 'p') continue; // process p's numPs++; } System.out.println("Found " + numPs + " p's in the string."); } }
Here is the output of this program:
Found 9 p's in the string.
To see this effect more clearly, try removing the continue
statement and recompiling. When you run the program again, the count will be wrong, saying that it found 35 p's instead of 9.
A labeled continue
statement skips the current iteration of an outer loop marked with the given label. The following example program, ContinueWithLabelDemo
, uses nested loops to search for a substring within another string. Two nested loops are required: one to iterate over the substring and one to iterate over the string being searched. The following program,
ContinueWithLabelDemo
, uses the labeled form of continue to skip an iteration in the outer loop.
class ContinueWithLabelDemo { public static void main(String[] args) { String searchMe = "Look for a substring in me"; String substring = "sub"; boolean foundIt = false; int max = searchMe.length() - substring.length(); test: for (int i = 0; i <= max; i++) { int n = substring.length(); int j = i; int k = 0; while (n-- != 0) { if (searchMe.charAt(j++) != substring.charAt(k++)) { continue test; } } foundIt = true; break test; } System.out.println(foundIt ? "Found it" : "Didn't find it"); } }
Here is the output from this program.
Found it
return
StatementThe last of the branching statements is the return
statement. The return
statement exits from the current method, and control flow returns to where the method was invoked. The return
statement has two forms: one that returns a value, and one that doesn't. To return a value, simply put the value (or an expression that calculates the value) after the return
keyword.
return ++count;
The data type of the returned value must match the type of the method's declared return value. When a method is declared void
, use the form of return
that doesn't return a value.
return;
The Classes and Objects lesson will cover everything you need to know about writing methods.