使用GeoSphere建立物件~~~(1) 預設存取等級且屬於不同套件~無法被繼承
(2) Final無法被繼承
(3) Interface函式都是public和abstract
(4) Interface函式不能是static
(5) Interface函式不能標註上final, strictfp, native
(6) 一個interface可以繼承多個其他interface
(7) Interface常數一定是public, final, static
(8) 預設和protected差不多
(9) 只有final修飾子可以用在區域變數
(10) Native就像抽象函式~以分號結尾
(11) 變數不能宣靠承strictfp
(12) Synchronized只用在函式
(13) strictfp只能用在類別跟函式
(14) native只能用在函式
(15) 介面不能實作介面
(16) Abstract函式須標示上abstract
(17) 介面可以extends介面
(18) PlayerPiece player= newPlayerPiece(); Object o =player; GameShpae shape = player; Animatable mover = player;
(19) 複寫函示可以拋出非可控異常(unchecked exception就是runtime exception)
(20) 複寫函示不可拋出新的可控異常~也不可以比原函示宣告的異常更廣
(21) 如果Dog implements Pet, Beagle extends Dog, Beagle IS-A Pet
(22) 實作interface的abstract函式要是public的或是預設
(23) 介面無法extends類別
(24) 介面無法implements介面
(25) Char相容於int
(26) 介面可做回傳型別
(27) 建構子不能回傳型別
(28) 抽象類別也有建構子
(29) 建構子永遠無法被繼承也不能複寫
(30) 建構子結束之前無法呼叫實體(非static)
(31) 建構子永遠不能呼叫super()又呼叫this()
(32) 建構子假如呼叫this()就不會呼叫super()
(33) 靜態函式不能存取非靜態(實體)變數
(34) 介面沒有建構子
(35) Static不能被覆寫~可是可以重新定義
(36) 抽象函式可以implements介面
(37) 超過陣列ArrayIndexOutOfBoundsException
(38) Null => NullPointerException
(39) Char可以放到int
(40) 介面可以做為參考型別
(41) 靜態區塊只能執行一次
(42) 實體區塊每建立一次執行一次
(43) 實體區塊是在建構子呼叫super()之後執行
(44) 在static裡出的錯誤ExceptionInitializerError
(45) 任何物件finalize()最多只能被資源回收器呼叫一次
(46) Object a = new int[3];
(47) 一些參考變數活在推疊內~另外一些活在推積內
(48) 執行finalize()時該物件就免除被GC的資格
(49) XOR在只有一個true才為true
(50) Switch接受char,short,int,long, 在java5內可用enum
(51) 所有非RuntimeException都被認為是可控式(checked)異常
(52) Java.lang.RuntimeException
(53) void xxx() throws IOException{}
(54) throw new IOException
(55) java.util.regex.Pattern
(56) java.util.regex.Matcher
(57) java.util.Scanner
(58) ??, 出現0或1
(59) *?, 出現0或多
(60) +?, 出現1或多
(61) 嘗試除以0 , ArithmeticException
(62) for(int x:y ) 不是 for(x : y)……….一定要定義
(63) ClassCastException , ExceptionInitializerError是由JVM拋出
(64) IllegalStateException通常被使用在回報環境的問題類似要去存取的資源已被關閉
(65) IllegalArgumentException通常由API拋出~當函式收到錯誤的引數時所拋出
(66) StringBuilder比較快~~~但沒有synchronized, StringBuffer有
(67) %[引數索引$][標記][寬度][.精確度]轉換字元
(68) 空白排在字元前~大寫字排在小寫字前
(69) 沒有＜? Implements Xxxxx＞
(70) Void foo(List＜? extends Serializable＞ list)
(71) Public void addAnimal(List＜? super Dog＞ animals)
(72) LinkedList有實作Queue所以有poll函式
(73) List是一個介面
(74) Map可以接受兩個型別參數
(75) Collections.reverseOrder 是 Comparator
(76) Collections.reverse(List＜?＞ list) 是 void
(77) Vector是舊版的ArrayList, 並擁有synchronized, 比ArrayList還慢
(78) TreeSet保證沒有重複~且存取的時候就會自然排序
(79) 函式-區域內飲類別不能加上存取修飾子
(80) 內隱類別可以用存取修飾子
(81) 靜態巢狀類別對外部類別的非static成員無法存取
(82) Thead.sleep()的exception, InterruptedException
(83) TreeSet保證沒重複, 且存取的時候就會自然排序
(84) 函式-區域內隱類別不能加上存取修飾子
(85) 內隱類別可以使用存取修飾子
(86) 靜態巢狀類別對外部類別的非static成員無法存取
(87) 如果執行緒呼叫wait()卻沒有鎖, 將會拋出IllegalMonitorStateException
(88) Thread靜態函式sleep(), yield() 非靜態join(), start()
(89) 只有物件可以同步化~~變數不行
(90) 任何物件都可以同步化~~但不要把static根this混用
(91) 當鎖被釋放時~~等待的執行緒不會回到可執行狀態~除非發出通知
(92) notifyAll(), notify(), wait()~~必須在同步化程式理呼叫
(93) 當執行緒想要呼叫wait()而等待~~會釋放他的鎖
(94) 執行緒想要呼叫物件的wait()必須要擁有該物件的鎖
(95) notify()並不會讓執行緒釋放他的鎖~~執行緒只有在離開同步化程式才會釋放鎖
(96) notifyAll()會通知所有等待一個特定物件的執行緒~不是等待任一物件的執行緒
(97) sleep()函式必須包在try/catch裡面
(98) 當Thread物件的start()被第二次呼叫~會拋出IllegalThreadStateException
(99) 實體函式和靜態函式用的是不同的鎖~所以不會互相卡住
(100) 同步化函式在同一個實體被呼叫~會互相卡住
(101) 同一個類別的同步化靜態函式會互相卡住~不論用哪個實體呼叫這些函式
(102) 好的OO設計追求鬆散耦合而避開緊密耦合 loose coupling
(103) 好的OO設計追求高內聚力而避開低內聚力 high cohesive
(104) Coupling 耦合
(105) Cohesive 內聚力
(106) Comparable 實做 int compareTo()
(107) Comparator 實作 int compare();
(108) Interface的實作~~只能預設或是public~~~實作一定要是public
(109)
Garbage collector
System.gc();
Runtime.getRuntime().gc();
Thead
public final static int MIN_PRIORITY = 1;
public final static int MAX_PRIORITY = 10;
int xx = 2;
for(int yy=2; yy>0;System.out.println(--yy)){
System.out.println(xx+" " +yy);
xx++;
}
output:
2 2
1
3 1
0
aLiveThread is runnalbe, which three guarantee that a thread will leave the running state?
wait();
sleep(1000);
aLiveThread.join();
一個檔案只有一個public物件
The wait() method is overloaded to accept a duration
Both wait() and notify() must be called from a synchronized context
Throw by JVM
StackOverflowError
NullPointerException
NoClassDefFoundError
ArrayIndexOutOfBoundException
Throw by developer
NumberFormatException
Sleep()不會釋放鎖
assert t<4>
不能放沒有回傳String或是int,short,long等等的函式
建構子沒有回傳東西
True
Good encapsulation helps promote loose coupling.
False
A class must be well encapsulated in order to be highly cohesive.
If two classes are NOT each highly cohesive, they cant’t be loosely coupled to each other.
High cohesive allows you to change a method’s implementation without having to change its API.(talk about encapsulation)
Tight coupling helps promote low cohesion.
Map只有put()沒有add()
List有add()沒有put()
When a thread invokes wait(), it realease its lock.
True
The java.io.BufferedReader class has a method to read a line of date at a time.
The java.io.FileRader has a read() method.
The java.io.BufferedReader class has a read() method.
A java.io.BufferedReader can be constructed with a java.io.FileReader instance.
False
A java.io.BufferedReader can be constructed with a java.io.FileReader instance.
The java.io.FileReader class has a method to read a line of date at a time.
True
JAR files placed in the /jre/lib/ext sub-directory within the J2SE directory tree be used by javac regardless of the command line classpath.
When a part of a directory tree that includes subdirectories with files is put into a JAR file, all of the files are saved in the JAR file , and the subdirectory structure is retained.
False
A JAR file can contain classes from only a single package.
JAR files can be used with the javac command but not with the java command.
In order to specify the use of JAR file on the command line, the JAR file’s name must NOT included in the classpath.
comma = 逗號
Which is true about using a DateFormat to print the value of a single Calendar object using different Locales?
True
You would use the DateFormat.format() method.
You would have to use a different DateFormat objects for each Locale you need to print.
You must convert the Calendar object to a Date object in order to send it to the DateFormat method printing.
False
You would use the DateFormat.parse() method.
You could use a single DateFormat object to handle all the Locales you need to print.
You can pass the Calendar object to the proper DateFormat method for printing.
Which can be constructed using an instance of java.io.File?
True
java.io.FileWriter
java.io.PrintWriter
java.io.FileReader
False
java.io.BufferedWriter
java.io.BufferedReader
interface Runnable{
public abstract void run();
}
Static variables are NOT serialized.
Transient variables are NOT serialized.
呼叫函式是呼叫該實體的函式
呼叫實體變數是呼叫該參考的變數
String qq = "";
String[] aa = {"-", "A", "."};
for(int x = 0; ++x <>
qq += aa[x];
System.out.println(qq);
}
java.util.ArrayList
java.util.LinkedHashSet
interface method can’t be final or static.
interface variables could be static.
True
is-a relationships always rely on inheritance.
is-a relationships always require at least two class types.
is-a relationships always rely on polymorphism.
False
is-a relationships always rely on instance variables.
is-a relationships are always tightly coupled.
