Java 嵌套类《二》 之 内部类

1.内部类可以作为一个帮助类实现：
public class DataStructure {
    // create an array
    private final static int SIZE = 15;
    private int[] arrayOfInts = new int[SIZE];
   
    public DataStructure() {
        // fill the array with ascending integer values
        for (int i = 0; i < SIZE; i++) {
            arrayOfInts[i] = i;
        }
    }
   
    public void printEven() {
        // print out values of even indices of the array
        InnerEvenIterator iterator = this.new InnerEvenIterator();
        while (iterator.hasNext()) {
            System.out.println(iterator.getNext() + " ");
        }
    }
   
    // inner class implements the Iterator pattern
    private class InnerEvenIterator {
        // start stepping through the array from the beginning
        private int next = 0;
       
        public boolean hasNext() {
            // check if a current element is the last in the array
            return (next <= SIZE - 1);
        }
       
        public int getNext() {
            // record a value of an even index of the array
            int retValue = arrayOfInts[next];
            //get the next even element
            next += 2;
            return retValue;
        }
    }
   
    public static void main(String s[]) {
        // fill the array with integer values and print out only
        // values of even indices
        DataStructure ds = new DataStructure();
        ds.printEven();
    }
}


2. Local and Anonymous Inner Classes
你可以把内部类声明在方法体里面，这样的内部类叫 local 内部类；
把一个内部类声明再方法体里面，并且不命名 叫 匿名内部类。
内部类的成员同样可以使用 private 、protected、public 或 package private 修饰符来修饰。