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CSE110 Lecture 13

CSE110 Lecture 13

Principles of Programming with Java
Loops: for statement
(202005)

Javier Gonzalez-Sanchez
PRO

June 06, 2017
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  1. CSE110
    Principles of Programming
    with Java
    Lecture 13:
    Loops: for statement
    Javier Gonzalez-Sanchez
    [email protected]
    javiergs.engineering.asu.edu | javiergs.com
    Office Hours: By appointment

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  2. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 2
    Topics
    class
    global
    variables
    methods statements
    instructions
    local
    variables
    conditional
    Statements
    if-else
    switch
    ?:
    loop
    Statement
    while
    do-while
    for

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  3. for Statement

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  4. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 4
    The for Statement
    The for statement has the following syntax:

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  5. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 5
    The for Statement
    • A for loop is functionally equivalent to the following
    while loop structure:
    //initialization
    while ( condition ) {
    // statement
    // increment or update
    }

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  6. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 6
    Example 1

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  7. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 7
    Logic of a for loop

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  8. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 8
    The for Statement
    • Like a while loop, the condition of a for statement is
    tested prior to executing the loop body
    • Therefore, the body of a for loop will execute zero
    or more times
    • It is well suited for executing a loop a specific
    number of times that can be determined in
    advance

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  9. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 9
    The for Statement
    Each expression in the header of a for loop is optional:
    • If the initialization is left out, no initialization is
    performed
    • If the condition is left out, it is always considered to
    be true, and therefore creates an infinite loop
    • If the increment is left out, no increment operation is
    performed
    Both semi-colons are always required in the for-loop
    header.

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  10. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 10
    Example 1

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  11. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 11
    Example 2

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  12. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 12
    Example 3

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  13. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 13
    Example 4
    for ( ; ; ) {
    System.out.println(”I am here! ");
    }

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  14. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 14
    Choosing a Loop Structure
    • When you can’t determine how many times you
    want to execute the loop body, use a while
    statement or a do statement
    • If it might be zero or more times, use a while
    statement
    • If it will be at least once, use a do statement

    If you can determine how many times you want to
    execute the loop body, use a for statement

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  15. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 15
    Nested loops
    • We can have a loop inside of another loop
    for (int i=1; i<=3; i=i+1) {
    for (int j=4; j>=1; j=j-1) {
    System.out.println( i + "," + j );
    }
    }

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  16. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 16
    One more thing
    • variable = variable + 1;
    variable++;
    • variable = variable - 1;
    variable--;

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  17. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 17
    One more thing
    • We can have a loop inside of another loop
    for (int i=1; i<=3; i++) {
    for (int j=4; j>=1; j--) {
    System.out.println( i + "," + j );
    }
    }

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  18. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 18
    Reference
    Chapter 4

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  19. CSE110 - Principles of Programming
    Javier Gonzalez-Sanchez
    [email protected]
    Summer 2020
    Disclaimer. These slides can only be used as study material for the class CSE110 at ASU. They cannot be distributed or used for another purpose.

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