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Master Java Arrays in 10 Minutes: Declaring, Initializing, and Accessing Array Elements

In just 10 minutes, this guide will teach you how to declare and initialize arrays in Java. You'll learn the syntax for different data types, such as `int[]`, `double[]`, and `String[]`, along with how to access and manipulate array elements. We'll cover explicit initialization, array indices, and common operations like traversing arrays with loops. By the end of this quick tutorial, you'll understand how to use arrays effectively in your Java programs.

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Master Java Arrays in 10 Minutes: Declaring, Initializing, and Accessing Array Elements

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  1. Java Arrays [Lists] in 10 Minutes

  2. Declaring an array (and its types) int[] myIntArray; double[] myDoubleArray; String[] myStrings; //What’s the pattern? //dataType[] arrayName; //Note: the arrays don’t really exist yet!

  3. Initializing an array int[] myIntArray = new int[4]; double[] myDoubleArray = new double[5]; String[] myStrings = new String[3]; //What’s the pattern? //dataType[] arrayName = new dataType[size]; //Now we’ve allocated new space for the arrays //Each array element has a default 0 value

  4. Explicit initialization //or we can explicitly initialize the arrays int[] myIntArray = { 4, 2, 6, 8 }; double[] myDoubleArray = { 1.0, 2.3, 6.3, 7.5, 0.1 }; String[] myStrings = {“lol”,“omg”,“ROTFLSHMSFOAIDMT”} //Note: use { } and separate elements with commas

  5. Size/length of an array int[] myIntArray = { 4, 2, 6, 8 }; System.out.println( myIntArray.length ); //prints 4 //Note: length has no () with arrays!!!!

  6. Accessing an array element int[] myIntArray = { 4, 2, 6, 8 }; System.out.print( myIntArray[0] ); //prints 4 System.out.print( myIntArray[2] ); //prints 6 System.out.print( myIntArray[myIntArray.length-1] ); //prints 8 //Each element in the array has an index //Indices start at 0 and end at length-1

  7. Changing/setting an array element int[] myIntArray = { 4, 2, 6, 8 }; myIntArray[0] = 9; //myIntArray now has [9, 2, 6, 8] myIntArray[1] = myIntArray[2]; //myIntArray now has [9, 6, 6, 8]

  8. Loops and arrays //Example of linear traversal of array int[] myIntArray = { 4, 2, 6, 8 }; for (int i = 0; i < myIntArray.length; i++) { System.out.println(myIntArray[i]); } //Try out on your own the same loop and print out all the words in: String[] myStrings = {“lol”,“omg”,“ROTFLSHMSFOAIDMT”}

  9. Initialize array elements with a loop //Traverse the array and set each element to 3 int[] myIntArray = { 4, 2, 6, 8 }; for (int i = 0; i < myIntArray.length; i++) { myIntArray[i] = 3; }

  10. Reference variables • Array variables are actually references to the arrays Example: int[] myIntArray = new int[4]; int[] array2 = myIntArray; //How many arrays are there? (Hint: How many times did we say “new”? //How many array references are there? (Hint: How many times did we say “int[]”?

  11. Reference Variables cont’d int[] myIntArray = { 4, 2, 6, 8 }; int[] array2 = myIntArray; array2[0] = 0; System.out.print(myIntArray[0]); //prints 0 //myIntArray and array2 “refer” to the same array

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