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AP Java

AP Java. Warm-up Boolean Array. class Exercise5 { public static void main ( String[] args ) { int [] val = {0, 1, 2, 3}; int temp; System.out.println ( "Original Array: " + val [0] + " " + val [1] + " " + val [2] + " " + val [3] );

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AP Java

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  1. AP Java Warm-up Boolean Array

  2. class Exercise5 { public static void main ( String[] args ) { int[] val = {0, 1, 2, 3}; int temp; System.out.println( "Original Array: " + val[0] + " " + val[1] + " " + val[2] + " " + val[3] ); // write the code to reverse the order of the numbers in the array System.out.println( "Reversed Array: " + val[0] + " " + val[1] + " " + val[2] + " " + val[3] ); } }

  3. Warm up Array Reading • Common Array Algorithms Link • Complete the fill in blanks on the web pages • Take notes as needed.

  4. Boolean Array Program (11/2/2015) • Show all prime numbers <=1000 • Use the sieve of Eratosthenes • Write a program to use this process in finding all primes less than or equal to 1000. • How many primes will Java let you find using this method? • Cross out 1, because it is not prime. • Circle 2, because it is the smallest positive even prime. Now cross out every multiple of 2; in other words, cross out every second number. • Circle 3, the next prime. Then cross out all of the multiples of 3; in other words, every third number. Some, like 6, may have already been crossed out because they are multiples of 2. • Circle the next open number, 5. Now cross out all of the multiples of 5, or every 5th number. • Continue doing this until all the numbers through 100 have either been circled or crossed out. You have just circled all the prime numbers from 1 to 100!

  5. Getting Started • Creating an array of Booleans • boolean[] seive = new boolean[1000]; • Initializing them to true (potentially prime). • for(inti = 0; i < seive.length; i++ ) • seive[i] = true ;

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