目前時間 in java

利用Calendar class
java.util.Calendar

ex: 顯示目前幾點
Calendar.getInstance().get(Calendar.HOUR_OF_DAY)
顯示目前幾分
Calendar.getInstance().get(Calendar.MINUTE)

JBuilder 指令

F3:
在function上按F3，進入定義此function之處。

JNI

檔名:
.jnilib : mac os x , prefixed by lib and suffixed with .jnilib
.so : solaris and linux
.dll: windows

in library file:
(1) include
(2) function格式:
ex: JNIEXPORT jint JNICALL Java_Test_show(JNIEnv *env, jobject rkObject)
function name = Java_Test_show, 以Java開頭，接著是溝通的Java的class name，最後才是function name
如果Java是在某個package上，要包含package name， 例如class Dog在package Animal下，
則完整的function name是Java_Animal_Dog_eat()
JNIEXPORT and JNICALL make this function to be found
(3)compile:
gcc -c -I /System/Library/Frameworks/JavaVM.framework/Headers test.c

如果是在xcode，在target info panel下的 build tab下的Header Search Paths設成/System/Library/Frameworks/JavaVM.framework/Headers
(4) product jnilib file
gcc -dynamiclib -o libtest.jnilib test.o -framework JavaVM


in Java
(1) check path, jnilib檔的位置要在path上
System.out.println( System.getProperty( "java.library.path" ) );
(2) loads the library named libhello.jnilib
System.loadLibrary("hello")
(3) 宣告要呼叫的library function
ex: public native void show();
以public native開頭


把Array 的結果copy back to 呼叫端
(*env)->ReleaseIntArrayElements(env, ctrllist, jBody, 0);

ShiftOne JRat

可trace Java程式運行過程中的function call。

如何trace
在觀察的java程式的VM arguments加上
-javaagent:shiftone-jrat.jar

jar

建jar檔
jar cvfm myJAR.jar manifest *.class

mainfest : 說明main在哪個class
Main-Class:<空一格>類別名稱
<空白行>

run多個jar檔:
java -cp x.jar:y.jar abc.mainApp
-cp後接相關的jar檔， mainApp表示main所在的class, abc表 mainApp所在的package

shark( profile program in MAC)

ex:
如果test是java的程式，
java -agentlib:Shark test 使得此程式可被shark觀看，
然後在shark的程式裡選擇start開始sample。
選擇java call trace可觀看程式運行時的function call呼叫情形。

java command 參數

-cp: class search path of directories and zip/jar files

native method

A native method is a Java method whose implementation is provided by non-java code

instanceof

判斷一個物件是否是某個type
ex: if(x instanceof Dog)

如果x的type是dog，and dog extends Animal
x instanceof Dog and x instanceof Animal are both true

如果y的type是Animal，
y instanceof Animal is ture. But y instanceof Dog is false

how to get resource

1. get Class object of the class that has resource

2. if resource is image or audio , use getResource(String name) to get resource as a URL.
Then read it with getImage or getAudioClip

3. other resource use getResourceAsStream(String name) to get InputStream to read.

property

The keys & values are strings

java.util.Properties

property file format:
key = value

ex:
Properties settings = new Properties();
settings.put("PROMPT", "$p$g");
settings.put("TEMP", "C:\\Windows\\Temp");
settings.put("CLASSPATH", "c:\\jdk\\lib;.");
settings.store(System.out, "Environment settings");

output:
#Environment settings
#Sun Jan 21 07:22:52 1996
CLASSPATH=c:\\jdk\\lib;.
TEMP=C:\\Windows\\Temp
PROMPT=$p$g

store(OutputStream out, String comments):
Writes this property list (key and element pairs) in this Properties table to the output stream

to load properties from a file:
FileInputStream in = new FileInputStream("text.properties");
settings.load(in);

use getProperty(String key) to get property

eclipse cvs

Synchronize with Repository
顯示本地端檔案與CVS的差異
Commit
將檔案更改送上CVS, 參考 Eclipse/CVS Commit
Update
更新本地端檔案, 參考 Eclipse/CVS Update

java compile 參數

-Xmx512m :
give java 512m memory