Exercise 4-3 (Method call Aliasing)

Chapter_4     Exercise_4-2

Exercise_4-4

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Exercise 4-3     TIJ, p. 67

Exercise 4-3: (1) Create a class containing a float and use it to demonstrate aliasing during method calls.

Aliasing.java

import static java.lang.System.out;

class Tank
{
float level;
}
// aliasing during method call (pass arguments by reference)
public class Aliasing
{
static void println(Object obj) {out.println(obj);}
static void changeLevel(Tank t, float newLevel) {t.level = newLevel;}

public static void main(String[] args)
{
Tank t = new Tank();
println("t.level: " + t.level); // initialized to 0.0f (float)

t.level = 9; // int to float OK, no precision loss
println("t.level: " + t.level); // 9.0f (printed 9.0)

// changeLevel(t, 27.0); // compile error, precision loss (from double)
changeLevel(t, 27.0f); // f for float, aliasing (t sent by reference)
println("t.level: " + t.level); // 27.0
}
}
/*
javac Aliasing.java
java Aliasing
t.level: 0.0
t.level: 9.0
t.level: 27.0
*/

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Chapter_4     Exercise 4-2

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