关于java数组length

 新建java数组时有多种方法，可new或跟c一样只用声明，如int[] a;另外值得注意的一点是，length方法只能返回数组大小，但数组有可能是空的（int是为null，char时为(char)0,boolean时为false），可能是空的基本数据类型，也可能是空对象

class Weeble{}

public class ArraySize {

      //private static Test monitor = new Test();

      public static void main(String[] args){

            Weeble[] a;

            Weeble[] b = new Weeble[5];

            Weeble[] c = new Weeble[4];

            for(int i=0;i<c.length;i++)

                  if(c[i] == null)

                        c[i] = new Weeble();

            Weeble[] d = {

                  new Weeble(), new Weeble(),new Weeble()   

            };

            a= new Weeble[]{

                        new Weeble(),new Weeble()

            };

            System.out.println("a.length="+a.length);

            System.out.println("b.length="+b.length);

            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);

            

            int[] e;

            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};

      //    System.out.println("e.length="+e.length);

            System.out.println("f.length="+f.length);

            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);

            

            

                  

            

            boolean[] q=new boolean[3];

            System.out.println("q.length="+q.length);

            for(int i=0;i<q.length;i++)

                  System.out.println("q["+i+"]="+q[i]);

            

            char t[]= new char[3];

            System.out.println("t.length="+t.length);

            for(int i=0;i<t.length;i++)

                  System.out.println("t["+i+"]="+t[i]);

            

            

      }

}

输出：

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

q.length=3

q[0]=false

q[1]=false

q[2]=false

t.length=3