6 Repetition Control Structures

Computer Programming 2 (Java) Repetition Control Structures

Repetition Control Structures  

Java statements that allows a programmer to e xecute specific blocks of code a number of times Include types such as: o While o Do-while o For

While structure The while loop is a statement or block of statements that is repeated as long as some condition  is satisfied. The general format of a while stateme nt is 

while (boolean _expression) { statement 1; statement 1; …  } Sample1: int counter = 1; while (counter <= 10) { System.out.println(“counter System.out.println(“coun ter = ” + counter) ; Counter += 1;  }

Sample2: int counter = 1; while (counter *counter < 10) { System.out.println(counterr * counter) ; System.out.println(counte Counter ++;  } Do-While Structure The do-while structure is similar to the while-loop. The statements inside a do-while loop are  executed several times as long as the condition is satisfied.  The general format of a do-while statement is: do { statement 1; statement 2; …  } while (boolean expression); expression);

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Computer Programming 2 (Java) Repetition Control Structures Sample1:

int x = 0; do { System.out.println ( “x = ”+ x);  x++  } while (x <10 ); Sample 2:

do { System.out.println ( “Hello”);  } while (false);

For Structure The for statement instructs a program to perform a block of code a specified number of times.  Syntax   for (initialization; condition; increment/decrement) { Statement1; Statement2; …  }

Sample1:

int x;  for (x = 1; x<=10; x++){ System.out.println (“ x= “ + x);  } Sample 2:

int i;  for (i = 1; i<=10; i++){ System.out.println (“I”);  } Branching Statements These statements redirect the flow of program execution  These include:  o Break o Continue o Return Break Statement The break statement causes an ex it from an enclosing loop. 

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Computer Programming 2 (Java) Repetition Control Structures  

In other words, encountering the break stateme nt causes immediate termination of the loop. Program control picks up at the co de following the loop.

Sample:  for(ctr = 1; ctr <=100; ++ctr) { System.out.println (“ \nctr = “ + ctr); if (ctr == 50) Break; 

This program segment will normally print all numbers between 1 to 100. But because of the break statement, only the numbers between 1 to 50 will be printed.

Continue Statement The continue statement works in a somewhat similar way to the break statement.  But instead of forcing loop termination, continue forces the next iteration for loop to take place,  skipping anycode in between.

Sample:  for (ctr = 1; ctr <= 100; ++ctr) { if (x% 2 != 0) continue; System.out.println (“ \n” + ctr);  } 

This program segment will print all even numbers between 1 to 100.

Return Statement The return statement is used to exit from the current method.  Flow of control returns to the statement that follows the original method call. 

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