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<<DB_Language.ppt>>
Database 實驗室專用程式語言
Java
Language - 2
Outline
Programming language chaos
一小時精通 Java 不是夢Java 環境設定
Language - 3
Laguage 的戰國時代
Delphi
Delphi
C
Basic
C++
Pascal
C
Java
Delphi
Language - 4
基本型態 & 運算式boolean
char 16-bit
byte 8-bit
short 16-bit
int 32-bit
long 64-bit
float 32-bit
double 64-bit
void
if…else
while
do…while
for loop
switch…case
++ 、 --
< 、 <= 、 > 、 >=
== 、 !=
&& 、 || 、
Language - 5
Say Hello in C
// Hello.c
#include <stdio.h>
int main(int argc, char* args[])
{
printf(“Hello!\n”);
return 0;
}
Language - 6
Class 類別
// Hello.java
public class Hello {
// …
}
Class 的宣告方式
檔案名稱必須和有 public 修飾字宣告的類別名稱一樣。
Language - 7
Say Hello in Java
// Hello.java
import java.lang.*;
public class Hello {
public static void main(String[] args) {
System.out.println(“Hello!”);
}
}
Language - 8
Java 編譯器javac.exe
% lsHello.java
% javac Hello.java
% lsHello.class Hello.java
% lsHello.java
% javac Hello.java
% lsHello.class Hello.java
Language - 9
Java 直譯器java.exe
啟動虛擬機器執行應用程式
% lsHello.class
% java HelloHello!
%
% lsHello.class
% java HelloHello!
%
Language - 10
Fibonacci Sequence
otherwise
nif
nFibnFib
nnFib
2
)1()2()(
0 1 2 3 4 5 6 7 8 9 10 …
0 1 1 2 3 5 8 13 21 34 55 …
0 1 2 3 4 5 6 7 8 9 10 …
0 1 1 2 3 5 8 13 21 34 55 …
Language - 11
Solution in C
// Fibonacci.c
#include <stdio.h>
int fib(int n)
{
if (n < 2)
return n;
else
return fib(n-2) + fib(n-1);
}
Language - 12
Fibonacci (Cont.)
// Fibonacci.c (cont.)
int main(int argc, char* args[])
{
printf(“%d\n”, fib(10)); // 55
return 0;
}
Language - 13
Solution in Java
// Fibonacci.java
import java.lang.*;
public class Fibonacci {
static int fib(int n) {
if (n < 2)
return n;
else
return fib(n-2) + fib(n-1);
}
// cont…
Language - 14
Fibonacci (Cont.)
// Fibonacci.java (cont.)
public static void main(String[] args) {
System.out.println(fib(10)); // 55
}
} // end class
Language - 15
Global Variable in C
// Global.c
#include <stdio.h>
int myScore = 0;
void increment() {
myScore = myScore + 1;
}
void incrementByTwo() {
myScore = myScore + 2;
}
Language - 16
Global in C (Cont.)// Global.c (cont.)
int main(int argc, char* args[])
{
increment();
printf("myScore = %d\n", myScore);
// myScore = 1
incrementByTwo();
printf("myScore = %d\n", myScore);
// myScore = 3
}
Language - 17
Global Variable in Java// Global.java
import java.lang.*;
public class Global {
static int myScore = 0;
static void increment() {
myScore = myScore + 1;
}
static void incrementByTwo() {
myScore = myScore + 2;
}
// cont…
Language - 18
Global in Java (Cont.)
// Global.java (cont.)
public static void main(String[] args) {
increment();
System.out.println("myScore = " + myScore);
incrementByTwo();
System.out.println("myScore = " + myScore);
}
} // end class
Language - 19
struct in C
// Person.c
#include <stdio.h>
struct Person
{
int height;
int weight;
};
// cont…
Language - 20
Struct in C (Cont.)
// Person.c (cont.)
int main(int argc, char* args[])
{
struct Person Jordan;
Jordan.height = 198;
Jordan.weight = 90;
printf("Height is %d\n", Jordan.height);
// Height is 198
printf("Weight is %d\n", Jordan.weight);
// Weight is 90
return 0;
}
Language - 21
class in Java
// PersonTest.java
import java.lang.*;
class Person {
int height = 0;
int weight = 0;
}
// cont…
Language - 22
class in Java// PersonTest.java (cont.)
public class PersonTest {
public static void main(String[] args){
Person Jordan = new Person();
Jordan.height = 198;
Jordan.weight = 90;
System.out.println("Height is " +
Jordan.height); // Height is 198
System.out.println("Weight is " +
Jordan.weight); // Weight is 90
}
} // end class
Language - 23
Types in Java
基本型態 (primitive type)
參考型態 (reference type)物件陣列
int grade = 89;
double PI = 3.14159;
Language - 24
建立與操控物件You must create all objects.
String son = new String(“Peter”);
You manipulate objects with reference.String son = new String(“Peter”);
int i = son.indexOf(“t”); // i = 2
物件和 reference 之間的關係，好比電視和遙控器之間的關係一樣。物件和 reference 之間的關係，好比電視和遙控器之間的關係一樣。
referencereference StringString
Language - 25
基礎型別的 Array
C
int grades[10];
grades[0] = 99;
grades[1] = 72;
int[] grades = new int[10];
grades[0] = 99;
grades[1] = 72;
Java
Java 中陣列的名稱只是一個 reference
Java 中陣列的名稱只是一個 reference
Language - 26
Array of Objects
String bird = new String(“bird”);
String[] pets = new String[4];
pets[0] = “dog”;
pets[1] = new String(“fish”);
pets[2] = bird;
// pets[3] = null
物件陣列的 element 是指向該物件的 reference ，而不是物件的真正實體，每個 element 的預設值都是 null。物件陣列的 element 是指向該物件的 reference ，而不是物件的真正實體，每個 element 的預設值都是 null。
Language - 27
Array of String 圖示
petspets
String[]
names[0]
names[1]
names[2]
names[3]
StringString
StringString
StringString
null
Language - 28
陣列的建立與初始化int[] primes = {2, 3, 5, 7, 7+4}; // primes[4] = 11
String[] children = {“Peter”, new String(“Sunny”)};
匿名陣列 (anonymous array)
void setPets(String[] pets) { // … }
String dog = “Dog”;
setPets( new String[]
{“Bird”, new String(“Fish”), dog} );
Language - 29
陣列的長度// ArrayLength.java
import java.lang.*;
public class ArrayLength {
public static void main(String[] args) {
showLength(new String[][] {
{"a", "b", "c"},
{"d", "e", "f"} } );
}
// cont…
Language - 30
陣列的長度 (Cont.)// ArrayLength.java (Cont.)
static void showLength(String[][] letters) {
System.out.println("letters is " +
letters.length); // 2
System.out.println("letters[0] is " +
letters[0].length); // 3
System.out.println("letters[1] is " +
letters[1].length); // 3
}
} // end class
Language - 31
陣列終極洗禮Java 視 array 為一個特殊的物件Java 使用 new 來配置陣列的實體Java 的 array 有一個專用的 field – length，用來表達陣列的長度
Language - 32
Java 環境設定下載 Java Development Kit (JDK)
http://java.sun.com
設定 Java_Home 環境變數更新 PATH 環境變數
PATH=%PATH%;%JAVA_HOME%\bin;
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