80 lines
2.2 KiB
Java
80 lines
2.2 KiB
Java
// arrays/ArrayOptions.java
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// (c)2017 MindView LLC: see Copyright.txt
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// We make no guarantees that this code is fit for any purpose.
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// Visit http://OnJava8.com for more book information.
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// Initialization & re-assignment of arrays
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import java.util.*;
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import static onjava.ArrayShow.*;
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public class ArrayOptions {
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public static void main(String[] args) {
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// Arrays of objects:
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BerylliumSphere[] a; // Local uninitialized variable
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BerylliumSphere[] b = new BerylliumSphere[5];
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// The references inside the array are
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// automatically initialized to null:
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show("b", b);
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BerylliumSphere[] c = new BerylliumSphere[4];
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for(int i = 0; i < c.length; i++)
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if(c[i] == null) // Can test for null reference
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c[i] = new BerylliumSphere();
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// Aggregate initialization:
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BerylliumSphere[] d = {
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new BerylliumSphere(),
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new BerylliumSphere(),
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new BerylliumSphere()
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};
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// Dynamic aggregate initialization:
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a = new BerylliumSphere[]{
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new BerylliumSphere(), new BerylliumSphere(),
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};
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// (Trailing comma is optional)
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System.out.println("a.length = " + a.length);
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System.out.println("b.length = " + b.length);
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System.out.println("c.length = " + c.length);
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System.out.println("d.length = " + d.length);
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a = d;
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System.out.println("a.length = " + a.length);
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// Arrays of primitives:
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int[] e; // Null reference
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int[] f = new int[5];
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// The primitives inside the array are
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// automatically initialized to zero:
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show("f", f);
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int[] g = new int[4];
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for(int i = 0; i < g.length; i++)
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g[i] = i*i;
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int[] h = { 11, 47, 93 };
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// Compile error: variable e not initialized:
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//- System.out.println("e.length = " + e.length);
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System.out.println("f.length = " + f.length);
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System.out.println("g.length = " + g.length);
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System.out.println("h.length = " + h.length);
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e = h;
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System.out.println("e.length = " + e.length);
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e = new int[]{ 1, 2 };
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System.out.println("e.length = " + e.length);
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}
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}
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/* Output:
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b: [null, null, null, null, null]
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a.length = 2
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b.length = 5
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c.length = 4
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d.length = 3
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a.length = 3
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f: [0, 0, 0, 0, 0]
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f.length = 5
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g.length = 4
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h.length = 3
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e.length = 3
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e.length = 2
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*/
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