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MSIS 6 55 Advanced Business Applications Programming

Week 7 Arrays. MSIS 6 55 Advanced Business Applications Programming. 7 . 1. Arrays. Data structures Related data items of same type Remain same size once created Fixed-length entries Group of variables Have same type Reference type. Fig. 7.1 | A 12-element array. Index.

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MSIS 6 55 Advanced Business Applications Programming

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  1. Week 7 Arrays MSIS 655Advanced Business Applications Programming 7.1

  2. Arrays • Data structures • Related data items of same type • Remain same size once created • Fixed-length entries • Group of variables • Have same type • Reference type

  3. Fig. 7.1 | A 12-element array.

  4. Index • Also called subscript • Position number in square brackets • Must be positive integer or integer expression • First element has index zero a = 5; b = 6; c[ a + b ] += 2; • Adds 2 to c[ 11 ] • c.length accesses array c’s length

  5. Declaring and Creating Arrays • Arrays are objects that occupy memory • Created dynamically with keyword new int c[] = newint[ 12 ]; • Equivalent toint c[]; // declare array variable c = newint[ 12 ]; // create array • We can create arrays of objects too String b[] = new String[ 100 ];

  6. Using an array initializer Use initializer list • Items enclosed in braces ({}) • Items in list separated by commas int n[] = { 10, 20, 30, 40, 50}; • Creates a five-element array • Index values of 0, 1, 2, 3, 4 • Do not need keyword new

  7. Enhanced for Statement • New feature of J2SE 5.0 • Allows iterates through elements of an array or a collection without using a counter • Syntax for ( parameter : arrayName ) statement

  8. Multidimensional Arrays • Multidimensional arrays • Tables with rows and columns • Two-dimensional array • m-by-n array

  9. Multidimensional Arrays (Cont.) • Declaring two-dimensional array b[2][2] int b[][] = { { 1, 2 }, { 3, 4 } }; • 1 and 2 initialize b[0][0] and b[0][1] • 3 and 4 initialize b[1][0] and b[1][1] int b[][] = { { 1, 2 }, { 3, 4, 5 } }; • row 0 contains elements 1 and 2 • row 1 contains elements 3, 4 and 5 • Lengths of rows in array are not required to be the same

  10. Multidimensional Arrays (Cont.) • Creating two-dimensional arrays with array-creation expressions • Can be created dynamically • 3-by-4 array int b[][]; b = newint[ 3 ][4 ]; • Rows can have different number of columns int b[][]; b = newint[ 2 ][ ]; // create 2 rows b[ 0 ] = newint[ 5 ]; // create 5 columns for row 0 b[ 1 ] = newint[ 3 ]; // create 3 columnsfor row 1

  11. Lab activities (Week 7) • Exercises (pp. 342-344)7.10, 7.11, 7.12, 7.17

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