vlambda博客
学习文章列表

public final class Boolean implements Serializable, Comparable<Boolean> { // 预先设置两个对象 public static final Boolean TRUE = new Boolean(true); public static final Boolean FALSE = new Boolean(false);
 public Boolean(boolean var1) { this.value = var1; }
 public Boolean(String var1) { this(parseBoolean(var1)); }
 // 工厂方法 public static Boolean valueOf(boolean var0) { return var0?TRUE:FALSE; // 返回预先设置的对象，而不是创建对象 } // 工厂方法 public static Boolean valueOf(String var0) { return parseBoolean(var0)?TRUE:FALSE; } // ... other code}

public class Collections { // 私有，典型工厂 private Collections() { }
 public static final List EMPTY_LIST = new EmptyList<>(); // 工厂方法 public static final <T> List<T> emptyList() { return (List<T>) EMPTY_LIST; } private static class EmptyList<E> extends AbstractList<E> implements RandomAccess, Serializable { // code }
 // 工厂方法 public static <E> List<E> checkedList(List<E> list, Class<E> type) { // 根据具体情况，获取相应子类 return (list instanceof RandomAccess ? new CheckedRandomAccessList<>(list, type) : new CheckedList<>(list, type)); }
 // 子类1 static class CheckedRandomAccessList<E> extends CheckedList<E> implements RandomAccess { CheckedRandomAccessList(List<E> list, Class<E> type) { super(list, type); }
 public List<E> subList(int fromIndex, int toIndex) { return new CheckedRandomAccessList<>( list.subList(fromIndex, toIndex), type); } }
 // 子类2 static class CheckedList<E> extends CheckedCollection<E> implements List<E> { // code }}

// 非Android中的AlertDialog，便于说明问题，举个例子public class AlertDialog { private int width; private int height; private String title; private String confirmText; private String denyText;
 private AlertDialog(){} public AlertDialog(int width, int height){ // 空白的警告框 AlertDialog(width,height,null); }
 // 带标题的警告框 public AlertDialog(int width, int height, String title){ // 带标题的警告框 AlertDialog(width, height, title, "确定"); }
 // 带标题的警告框，有确定按钮 public AlertDialog(int width, int height, String title, String confirm){  AlertDialog(width, height, title, confirm, null); }
 // 带标题的警告框，有确定按钮，取消按钮 public AlertDialog(int width, int height, String title, String confirm, String denyText){ // set every thing. }}

// 非Android中的AlertDialog，便于说明问题，举个例子public class AlertDialog { private int width; private int height; private String title; private String confirmText; private String denyText;
 public AlertDialog(){}// 空白的构造函数
 public void setWidth(int width){ this.width = width; } // 其他set方法}

// 非Android中的AlertDialog，便于说明问题，举个例子public class AlertDialog { private int width; private int height; private String title; private String confirmText; private String denyText;
 // private private AlertDialog(){}
 // Builder中使用 protected AlertDialog(Builder b){ width = b.width; height = b.height; // ..... if(width==0||height==0) throws new Exception("size must be set"); }
 // 构造器 public static class Builder { private int width; private int height; private String title; private String confirmText; private String denyText;
 // 注意：返回的Builder。 public Builder setTitle(String title) { this.title = title; return this; } // 其他set...
 public AlertDialog build(){ return AlertDialog(this); } }}

public class Elvis{ // 注意，公有final对象 public static final Elvis INSTANCE = new Elvis(); private Elvis(){}}

public class Util{ private Util(){ // 抛出异常，防止内部误调用 throw new AssertionError(); }}

public class Stack{ private Object[] elements; private int size = 0; private static final int DEFAULT_INITIAL_CAPACITY = 16;
 public Stack(){ elements = new Object[DEFAULT_INITIAL_CAPACITY]; }
 public void push(Object e){ ensureCapacity(); elements[size++]=e; // allocate新的堆内存和栈内存 }
 public Object pop(){ if(size==0) throw new EmptyStackException(); return element[--size]; // pop出element[size]，该对象不再有效。内存泄漏原因。 }
 private void ensureCapacity(){ if(elements.length==size) elements = Arrays.copyOf(elements, 2*size+1); }}

public Object pop(){ if(size==0) throw new EmptyStackException(); elements[size] = null; // 等待回收 return element[--size]; }

public Object pop(){ if(size==0) throw new EmptyStackException(); elements[size] = null; // 等待回收 return element[--size]; }

private static final Thing[] PRIVATE_VALUES = {...}// 此时获取到的才是“常量”public static final List<Thing> VALUS =  Collections.unmodifiableList(Arrays.asList(PRIVATE_VALUES))

private static final Thing[] PRIVATE_VALUES = {...}// 此时获取到的才是“常量”public static final Thing[] values(){ return PRIVATE_VALUES.clone();}

// Fails at runtimeObject[] objectArray = new Long[1];objectArray[0] = "I don't fit in"; // throw exception
// won't compileList<Object> ol = new ArrayList<Long>(); // Incompatible typesol.add("I don't fit in");

//public class Stack<E>{// public Stack();// public void push(E e);// public E pop();// public boolean isEmpty();//}
public void pushAll(Iterator<? extends E> src){ for(E e : src) push(e);}
public void popAll(Collection<? super E> dst){ while(!isEmpty()){ dst.add(pop()); }}
// Get and Put Principle

public enum Apple { FUJI, PIPPIN, GRANNY_SMITH }public enum Orange { NAVEL, TEMPLE, BLOOD }

// bad solutionpublic enum Ensemble { SOLO, DUET, TRIO, QUARTET, QUINTET,  SEXTET, SEPTET, OCTET, NONET, DECTET;
 public int numberOfMusicians() { return ordinal() + 1; }}// 
// improvementpublic enum Ensemble { SOLO(1), DUET(2), TRIO(3), QUARTET(4), QUINTET(5),  SEXTET(6), SEPTET(7), OCTET(8), NONET(9), DECTET(10), TRIPLE_QUARTET(12);
 private final int numberOfMusicians; Ensemble(int size) { this.numberOfMusicians = size; } public int numberOfMusicians() { return numberOfMusicians; }}

public Period(Date start, Date end){ this.start = new Date(start); // 使用了值的拷贝，没有使用原对象（指针） this.end = new Date(end); if(this.start.compareTo(this.end)>0) throw new IllegalArgumentException(start + " after " + end)}

public Date start(){ return new Date(start);}
public Date end(){ return new Date(end);}