Core Java Programming Language (JSE) : Chapter V - Arrays
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This document covers the creation and manipulation of arrays in Java, including declaration, initialization, and copying of array elements. It discusses single and multidimensional arrays, the constraints on resizing them, and introduces the enhanced for loop for iteration. Additionally, it provides code examples for various array operations and outlines the basic structure of array handling in Java.
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Creating Arrays
Use the new keyword to create an array object.
For example, a primitive (char) array:
public char[] createArray() {
char[] s;
s = new char[26];
for ( int i=0; i<26; i++ ) {
s[i] = (char) (âAâ + i);
}
return s;
}](https://image.slidesharecdn.com/005javasearrays-190430055819/85/Core-Java-Programming-Language-JSE-Chapter-V-Arrays-3-320.jpg)
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Creating Reference Arrays
Another example, an object array:
public Point[] createArray() {
Point[] p;
p = new Point[10];
for ( int i=0; i<10; i++ ) {
p[i] = new Point(i, i+1);
}
return p;
}](https://image.slidesharecdn.com/005javasearrays-190430055819/85/Core-Java-Programming-Language-JSE-Chapter-V-Arrays-5-320.jpg)
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Initializing Arrays
â Initialize an array element.
â Create an array with initial values.
String[] names;
names = new String[3];
names[0] = "Georgianna";
names[1] = "Jen";
names[2] = "Simon";](https://image.slidesharecdn.com/005javasearrays-190430055819/85/Core-Java-Programming-Language-JSE-Chapter-V-Arrays-6-320.jpg)
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Multidimensional Arrays
â Arrays of arrays:
int[][] twoDim = new int[4][];
twoDim[0] = new int[5];
twoDim[1] = new int[5];
int[][] twoDim = new int[][4]; // illegal
â Array of four arrays of five integers each:
int[][] twoDim = new int[4][5];](https://image.slidesharecdn.com/005javasearrays-190430055819/85/Core-Java-Programming-Language-JSE-Chapter-V-Arrays-7-320.jpg)
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Array Bounds
All array subscripts begin at 0:
public void printElements(int[] list) {
for (int i = 0; i < list.length; i++) {
System.out.println(list[i]);
}
}](https://image.slidesharecdn.com/005javasearrays-190430055819/85/Core-Java-Programming-Language-JSE-Chapter-V-Arrays-8-320.jpg)
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Using the Enhanced
for Loop
â Java 2 Platform, Standard Edition (J2SETM) version 5.0 introduced
an enhanced for loop for iterating over arrays:
public void printElements(int[] list) {
for ( int element : list ) {
System.out.println(element);
}
}](https://image.slidesharecdn.com/005javasearrays-190430055819/85/Core-Java-Programming-Language-JSE-Chapter-V-Arrays-9-320.jpg)
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Array Resizing
â You cannot resize an array.
â You can use the same reference variable to refer to an entirely new
array, such as:
int[] myArray = new int[6];
myArray = new int[10];](https://image.slidesharecdn.com/005javasearrays-190430055819/85/Core-Java-Programming-Language-JSE-Chapter-V-Arrays-10-320.jpg)
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Copying Arrays
The System.arraycopy() method to copy arrays is:
//original array
int[] myArray = { 1, 2, 3, 4, 5, 6 };
// new larger array
int[] hold = { 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 };
// copy all of the myArray array to the hold
// array, starting with the 0th index
System.arraycopy(myArray, 0, hold, 0, myArray.length);](https://image.slidesharecdn.com/005javasearrays-190430055819/85/Core-Java-Programming-Language-JSE-Chapter-V-Arrays-11-320.jpg)
Core Java Programming Language (JSE) : Chapter V - Arrays
- 1. Java Programming Language SE â 6 Module 5 : Arrays
- 2. www.webstackacademy.com Objectives â Declare and create arrays of primitive, class, or array types â Explain why elements of an array are initialized â Explain how to initialize the elements of an array â Determine the number of elements in an array â Create a multidimensional array â Write code to copy array values from one array to another
- 3. www.webstackacademy.com Creating Arrays Use the new keyword to create an array object. For example, a primitive (char) array: public char[] createArray() { char[] s; s = new char[26]; for ( int i=0; i<26; i++ ) { s[i] = (char) (âAâ + i); } return s; }
- 4. www.webstackacademy.com Creating an Array of Character Primitives
- 5. www.webstackacademy.com Creating Reference Arrays Another example, an object array: public Point[] createArray() { Point[] p; p = new Point[10]; for ( int i=0; i<10; i++ ) { p[i] = new Point(i, i+1); } return p; }
- 6. www.webstackacademy.com Initializing Arrays â Initialize an array element. â Create an array with initial values. String[] names; names = new String[3]; names[0] = "Georgianna"; names[1] = "Jen"; names[2] = "Simon";
- 7. www.webstackacademy.com Multidimensional Arrays â Arrays of arrays: int[][] twoDim = new int[4][]; twoDim[0] = new int[5]; twoDim[1] = new int[5]; int[][] twoDim = new int[][4]; // illegal â Array of four arrays of five integers each: int[][] twoDim = new int[4][5];
- 8. www.webstackacademy.com Array Bounds All array subscripts begin at 0: public void printElements(int[] list) { for (int i = 0; i < list.length; i++) { System.out.println(list[i]); } }
- 9. www.webstackacademy.com Using the Enhanced for Loop â Java 2 Platform, Standard Edition (J2SETM) version 5.0 introduced an enhanced for loop for iterating over arrays: public void printElements(int[] list) { for ( int element : list ) { System.out.println(element); } }
- 10. www.webstackacademy.com Array Resizing â You cannot resize an array. â You can use the same reference variable to refer to an entirely new array, such as: int[] myArray = new int[6]; myArray = new int[10];
- 11. www.webstackacademy.com Copying Arrays The System.arraycopy() method to copy arrays is: //original array int[] myArray = { 1, 2, 3, 4, 5, 6 }; // new larger array int[] hold = { 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 }; // copy all of the myArray array to the hold // array, starting with the 0th index System.arraycopy(myArray, 0, hold, 0, myArray.length);
- 12. www.webstackacademy.com Web Stack Academy (P) Ltd #83, Farah Towers, 1st floor,MG Road, Bangalore â 560001 M: +91-80-4128 9576 T: +91-98862 69112 E: [email protected]