Java编程思想学习笔记（三）
Java编程思想学习笔记（三）
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（美） Bruce Eckel 著 《Java编程思想》部分学习日记（随手记录的笔记）
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interface Selector{ boolean end(); Object current(); void next();}public class Sequence { private Object[] items; private int next =0; public Sequence(int size) { items=new Object[size]; } public void add(Object x) { if (next<items.length) { items[next++]=x; } } public class SequenceSelector implements Selector{ private int i=0; @Override public Object current() { return items[i]; } @Override public boolean end() { return i==items.length; } @Override public void next() { if (i<items.length) { i++; } } } public static void main(String[] args) { Sequence sequence =new Sequence(10); for (int i = 0; i < 10; i++) { sequence.add(Integer.toString(i)); } Selector selector =sequence.new SequenceSelector(); while(!selector.end()){ System.out.println(selector.current()+""); selector.next(); } }}
??其中：Selector selector =sequence.new SequenceSelector();
?? 为创建内部类对象。
?? 如果需要生成对外部类对象的引用，可以使用外部类的名字后面紧跟圆点和this。
public class DotThis { void f(){System.out.println("DotThis.f()");} public class Inner{ public DotThis outer() { return DotThis.this; } } public Inner inner() { return new Inner(); } public static void main(String[] args) { DotThis dotThis =new DotThis(); DotThis.Inner dtInner =dotThis.inner(); dtInner.outer().f(); }}?
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interface Contents{ int value();}public class Parcel7 { public Contents contents() { return new Contents() { private int i =11; public int value() { return i; } }; } public static void main(String[] args) { Parcel7 parcel7 =new Parcel7(); Contents contents= parcel7.contents(); }}等价于：package zengxiao;interface Contents{ int value();}public class Parcel7 { class MyContent implements Contents{ @Override public int value() { return 0; } }; public Contents contents() { return new MyContent(); } public static void main(String[] args) { Parcel7 parcel7 =new Parcel7(); Contents contents= parcel7.contents(); }}?
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public class Statistics { public static void main(String[] args) { Random rand =new Random(47); Map<Integer, Integer> map =new HashMap<Integer, Integer>(); for (int i = 0; i < 10000; i++) { int r =rand.nextInt(20); Integer freq =map.get(r); map.put(r, freq==null?1:freq+1); } System.out.println(map); }}?
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import java.util.LinkedList;public class Stack<T> { private LinkedList<T> storage =new LinkedList<T>(); public void push(T v){storage.addFirst(v);} public T peek() { return storage.getFirst(); } public T pop() { return storage.removeFirst(); } public Boolean empty() { return storage.isEmpty(); } public String toString() { return storage.toString(); }}public class StackTest { public static void main(String[] args) { Stack<String> stack = new Stack<String>(); for (String s : "my dog has fleas".split(" ")) { stack.push(s); } while (!stack.empty()) { System.out.println(stack.pop()+""); } }}?? Set
?? 不保存重复的元素。查找成为了set最重要的操作。，hashSet专门对快速查找进行了优化。如果想对结果进行排序的话建议使用TreeSet来代替HashSet
?? Queue
队列是一个典型的先进先出（FIFO）的容器。
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import java.util.ArrayList;import java.util.Arrays;import java.util.Collections;import java.util.List;public class zeng { public static void main(String[] args) { List<Integer> colList = new ArrayList<Integer>(); Integer[] moreInts = { 1, 2, 3, 4, 5 }; Collections.addAll(colList, moreInts); for (Integer integer : moreInts) { System.out.println(integer); } List<Integer> list = Arrays.asList(moreInts); for (Integer integer : list) { System.out.println(integer); } }}?