arraysize.java

think in java TIJ-3rd-edition-code.zip

//: c09:ArraySize.java
// Initialization & re-assignment of arrays.
import com.bruceeckel.simpletest.*;

class Weeble {} // A small mythical creature

public class ArraySize {
  public static void main(String[] args) {
    SimpleTest monitor =
      new SimpleTest("ArraySize");
    // Arrays of objects:
    Weeble[] a; // Null reference
    Weeble[] b = new Weeble[5]; // Null references
    Weeble[] c = new Weeble[4];
    for(int i = 0; i < c.length; i++)
      c[i] = new Weeble();
    // Aggregate initialization:
    Weeble[] d = { 
      new Weeble(), new Weeble(), new Weeble()
    };
    // Dynamic aggregate initialization:
    a = new Weeble[] {
      new Weeble(), new Weeble()
    };
    System.out.println("a.length=" + a.length);
    System.out.println("b.length = " + b.length);
    // The references inside the array are 
    // automatically initialized to null:
    for(int i = 0; i < b.length; i++)
      System.out.println("b[" + i + "]=" + b[i]);
    System.out.println("c.length = " + c.length);
    System.out.println("d.length = " + d.length);
    a = d;
    System.out.println("a.length = " + a.length);

    // Arrays of primitives:
    int[] e; // Null reference
    int[] f = new int[5];
    int[] g = new int[4];
    for(int i = 0; i < g.length; i++)
      g[i] = i*i;
    int[] h = { 11, 47, 93 };
    // Compile error: variable e not initialized:
    //!System.out.println("e.length=" + e.length);
    System.out.println("f.length = " + f.length);
    // The primitives inside the array are
    // automatically initialized to zero:
    for(int i = 0; i < f.length; i++)
      System.out.println("f[" + i + "]=" + f[i]);
    System.out.println("g.length = " + g.length);
    System.out.println("h.length = " + h.length);
    e = h;
    System.out.println("e.length = " + e.length);
    e = new int[] { 1, 2 };
    System.out.println("e.length = " + e.length);
    monitor.expect(new String[] {
      "a.length=2",
      "b.length = 5",
      "b[0]=null",
      "b[1]=null",
      "b[2]=null",
      "b[3]=null",
      "b[4]=null",
      "c.length = 4",
      "d.length = 3",
      "a.length = 3",
      "f.length = 5",
      "f[0]=0",
      "f[1]=0",
      "f[2]=0",
      "f[3]=0",
      "f[4]=0",
      "g.length = 4",
      "h.length = 3",
      "e.length = 3",
      "e.length = 2"
    });
  }
} ///:~