CS141: Topics for the Week of Oct 31, 2011

Topics & Activities

• Mon: Go over Technews assignment. No Technews next week!

• Chapter 6: Arrays and Array Lists
  • Declaring: int[] myNums; // creates only a reference!
  • Initializing/Creating elements: // size is always fixed.
    • myNums = new int[10];
    • myNums = { 0,1,2,... };
  • Setting the values:
    • Individual elements: myNums[3] = 255;
    • Using a loop to set entire arrays:
      • for (int i=0; i<myNums.length; i++) myNums[i] = 10;
      • using the fill method in the java.util.Arrays class: Arrays.fill(myNums,10);
  • Copying arrays: Beware!
    • int[] myNums2 = myNums; // does not make a copy!!
    • use loop or Arrays.copyOf
  • Enhanced loop: for (int element: myNums) sum = sum + element; // don't use to modify the array element values!
  • Other: summing, searching, max/min, inserting elements, removing elements, sorting, etc
  • Passing arrays as parameters in methods !!! Copy by reference vs Copy by value
  • 2D Arrays.

• Examples:

  • GUI Card Example (from last week) - modify to use an array to represent the names of suits.
  • Five-letter Words: the data file: words5.txt, the starting code FiveLetterWordsSkeleton.java
  • Salem average min/max temperatures: the data file aveMonthlyTemps.txt and the starting code TemperaturesSkeleton.java

• In Lab:

  • Follow the instructions: Lab 9: Arrays

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