绿色版jdk1.5.0 绿色(sè)版,直接(jiē)解压(yā)就行.给自己mark使用.
自(zì)动实现装箱和解箱操作(Boxing/Unboxing Conversions)
说明:实现(xiàn)了基本类型与外覆类之间(jiān)的(de)隐(yǐn)式转(zhuǎn)换(huàn)。基(jī)本类型(xíng)至外覆类的转换称为装(zhuāng)箱,外覆类至(zhì)基本类型的转换为解箱。这些类包(bāo)括
Primitive Type Reference Type
boolean Boolean
byte Byte
char Character
short Short
int Integer
long Long
float Float
double Double
例如,旧的实现方式
Integer intObject;
int intPrimitive;
ArrayList arrayList = new ArrayList();
intPrimitive = 11;
intObject = new Integer(intPrimitive);
arrayList.put(intObject); // 不能放入int类型,只(zhī)能使Integer
新的实现方式
int intPrimitive;
ArrayList arrayList = new ArrayList();
intPrimitive = 11;
//在这里intPrimitive被(bèi)自动的转换为Integer类(lèi)型(xíng)
arrayList.put(intPrimitive);
5静态(tài)导入(Static Imports)
很简(jiǎn)单的东(dōng)西,看(kàn)一个例子:
没有静(jìng)态导(dǎo)入
Math.sqrt(Math.pow(x, 2) + Math.pow(y, 2));
有了静态导入
import static java.lang.Math.*;
sqrt(pow(x, 2) + pow(y, 2));
其(qí)中import static java.lang.Math.*;就是静态导入的语法,它(tā)的意(yì)思是(shì)导入Math类中的所有static方法和属性(xìng)。这样(yàng)我们在使用(yòng)这些方法和属性时就不必写类名。
需(xū)要注意的(de)是默(mò)认(rèn)包(bāo)无法用静(jìng)态导(dǎo)入,另外如果导入的类中有(yǒu)重复的方法和属(shǔ)性(xìng)则需要写出类名,否(fǒu)则(zé)编译时无法通过。
6枚举类(Enumeration Classes)
用(yòng)法:public enum Name {types, ….}
简单的例子:
public enum Colors {Red, Yellow, Blue, Orange, Green, Purple, Brown, Black}
public static void main(String[] args){
Colors myColor = Colors.Red;
System.out.println(myColor);
}
又一个简单例子(zǐ):
import java.util.*;
enum OperatingSystems {windows, unix, linux, macintosh}
public class EnumExample1 {
public static void main(String args[]) {
OperatingSystems os;
os = OperatingSystems.windows;
switch(os) {
case windows:
System.out.println(“You chose Windows!”);
break;
case unix:
System.out.println(“You chose Unix!”);
break;
case linux:
System.out.println(“You chose Linux!”);
break;
case macintosh:
System.out.println(“You chose Macintosh!”);
break;
default:
System.out.println(“I don’t know your OS.”);
break;
}
}
}
应运enum简写的例子(zǐ):
import java.util.*;
public class EnumTest
{
public static void main(String[] args)
{
Scanner in = new Scanner(System.in);
System.out.print("Enter a size: (SMALL, MEDIUM, LARGE, EXTRA_LARGE) ");
String input = in.next().toUpperCase();
Size size = Enum.valueOf(Size.class, input);
System.out.println("size=" + size);
System.out.println("abbreviation=" + size.getAbbreviation());
if (size == Size.EXTRA_LARGE)
System.out.println("Good job--you paid attention to the _.");
}
}
enum Size
{
SMALL("S"), MEDIUM("M"), LARGE("L"), EXTRA_LARGE("XL");
private Size(String abbreviation) { this.abbreviation = abbreviation; }
public String getAbbreviation() { return abbreviation; }
private String abbreviation;
}
enum类中拥(yōng)有方法的一个例子:
enum ProgramFlags {
showErrors(0x01),
includeFileOutput(0x02),
useAlternateProcessor(0x04);
private int bit;
ProgramFlags(int bitNumber) {
bit = bitNumber;
}
public int getBitNumber() {
return(bit);
}
}
public class EnumBitmapExample {
public static void main(String args[]) {
ProgramFlags flag = ProgramFlags.showErrors;
System.out.println(“Flag selected is: “ +
flag.ordinal() +
“ which is “ +
flag.name());
}
}
7元数据(Meta data)
请参考
http://www-900.ibm.com/developerWorks/cn/java/j-annotate1/
http://www-900.ibm.com/developerworks/cn/java/j-annotate2.shtml
8Building Strings(StringBuilder类)
在JDK5.0中引入了StringBuilder类,该类(lèi)的(de)方(fāng)法不(bú)是同步(synchronized)的,这使得它比(bǐ)StringBuffer更加轻(qīng)量级(jí)和有效。
9控制台输入(Console Input)
在JDK5.0之前(qián)我(wǒ)们只能通过(guò)JOptionPane.showInputDialog进行输入,但在5.0中(zhōng)我(wǒ)们可(kě)以通过类Scanner在(zài)控制台进行输(shū)入操作
例如(rú)在1.4中的输入
String input = JOptionPane.showInputDialog(prompt);
int n = Integer.parseInt(input);
double x = Double.parseDouble(input);
s = input;
在(zài)5.0中我们可以
Scanner in = new Scanner(System.in);
System.out.print(prompt);
int n = in.nextInt();
double x = in.nextDouble();
String s = in.nextLine();
10Covariant Return Types(不晓得怎么(me)翻译,大概(gài)是 改变返回类型)
JDK5之前(qián)我们覆(fù)盖一个方(fāng)法时我(wǒ)们无法改变被方法的返回类型,但在JDK5中我们可(kě)以(yǐ)改变(biàn)它
例如(rú)1.4中我们只(zhī)能
public Object clone() { ... }
...
Employee cloned = (Employee) e.clone();
但是在5.0中我们可以改变返回类型为Employee
public Employee clone() { ... }
...
Employee cloned = e.clone();
11格式化I/O(Formatted I/O)
增加了类(lèi)似(sì)C的格式化输入(rù)输出,简单的例子(zǐ):
public class TestFormat{
public static void main(String[] args){
int a = 150000, b = 10;
float c = 5.0101f, d = 3.14f;
System.out.printf("%4d %4d%n", a, b);
System.out.printf("%x %x%n", a, b);
System.out.printf("%3.2f %1.1f%n", c, d);
System.out.printf("%1.3e %1.3e%n", c, d*100);
}
}
输出结果为:
150000 10
249f0 a
5.01 3.1
5.010e+00 3.140e+02
