09-linked_nodes - CSE143 Lecture9 ReferencesandLinkedNodes...

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CSE 143 Lecture 9 References and Linked Nodes reading: 16.1;  3.3 slides created by Marty Stepp http://www.cs.washington.edu/143/
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2 swap  method? Does the following  swap  method work?  Why or why not? public static void main(String[] args) { int a = 7; int b = 35; // swap a with b swap(a, b); System.out.println(a + " " + b); } public static void swap(int a, int b) { int temp = a; a = b; b = temp; }
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3 Value semantics value semantics : Behavior where values are copied when  assigned to each other or passed as parameters. When one primitive is assigned to another, its value is copied. Modifying the value of one variable does not affect others. int x = 5; int y = x ; // x = 5, y = 5 y = 17; // x = 5, y = 17 x = 8; // x = 8, y = 17
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4 Reference semantics reference semantics : Behavior where variables actually store  the address of an object in memory. When one reference variable is assigned to another, the object is  not  copied; both variables refer to the  same object . int[] a1 = {4, 5, 2, 12, 14, 14, 9}; int[] a2 = a1 ; // refers to same array as a1 a2[0] = 7; System.out.println( a1[0] ); // 7 index 0 1 2 3 4 5 6 value 5 2 12 14 14 9 0 7 a1 a2
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5 References and objects In Java, objects and arrays use reference semantics.  Why? efficiency. Copying large objects slows down a program. sharing. It's useful to share an object's data among methods. DrawingPanel panel1 = new DrawingPanel(80, 50); DrawingPanel panel2 = panel1; // same window panel2.setBackground(Color.CYAN); panel1 panel2
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6 References as fields Objects can store references to other objects as fields.
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This note was uploaded on 01/04/2011 for the course CSE 143 taught by Professor Sr during the Spring '08 term at University of Washington.

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09-linked_nodes - CSE143 Lecture9 ReferencesandLinkedNodes...

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