从2006到现在等待了多年的jdk7终于发布了.这里将对它的一些新特做一些初步的研究:
jdk7 相对于jdk6主要在以一几个方面有了非常显著的改进的提升:
首先分析其对java语言本身的改进:
二进制表示的支持(Binary Literals)的支持。
在JDK7中可以用二进制的形式表示整形数据（byte,short,int,long)，这些整形类数据如果用二制表示则需0b或0B打头。如：
byte aByte=(byte)0b01;
short aShort=(short)0B001;
int aInt=0b01001;
long aLong=0B011101L;
使用二进制表示数据有什么好处呢？我们看一下下面的例字。
示例一：
要求定义一个数组。表示按位旋转（即后个数是前一个数向左旋转一位，请注意是旋转）。用二制可以比较清晰地表示这种数据结构：
public static final int[] phases = {
0b00110001,
0b01100010,
0b11000100,
0b10001001,
0b00010011,
0b00100110,
0b01001100,
0b10011000
}
大家看了上面的定义可以比较快地理解定义的内容。如果用16进制或8进制那可能就比较难理解了。如下：
public static final int[] phases = {
0x31, 0x62, 0xC4, 0x89, 0x13, 0x26, 0x4C, 0x98
}
在定义和设计一些模拟器，如微处理器等方面也很有帮助。如下面是定义的一个8位的微处理器的模拟器：
public State decodeInstruction(int instruction, State state) {
if ((instruction & 0b11100000) == 0b00000000) {
final int register = instruction & 0b00001111;
switch (instruction & 0b11110000) {
case 0b00000000: return state.nop();
case 0b00010000: return state.copyAccumTo(register);
case 0b00100000: return state.addToAccum(register);
case 0b00110000: return state.subFromAccum(register);
case 0b01000000: return state.multiplyAccumBy(register);
case 0b01010000: return state.divideAccumBy(register);
case 0b01100000: return state.setAccumFrom(register);
case 0b01110000: return state.returnFromCall();
default: throw new IllegalArgumentException();
}
} else {
final int address = instruction & 0b00011111;
switch (instruction & 0b11100000) {
case 0b00100000: return state.jumpTo(address);
case 0b01000000: return state.jumpIfAccumZeroTo(address);
case 0b01000000: return state.jumpIfAccumNonzeroTo(address);
case 0b01100000: return state.setAccumFromMemory(address);
case 0b10100000: return state.writeAccumToMemory(address);
case 0b11000000: return state.callTo(address);
default: throw new IllegalArgumentException();
}
}
}
当然你可以很利二进制定义一张图片。如：
public static final short[] HAPPY_FACE = {
(short)0b0000011111100000;
(short)0b0000100000010000;
(short)0b0001000000001000;
(short)0b0010000000000100;
(short)0b0100000000000010;
(short)0b1000011001100001;
(short)0b1000011001100001;
(short)0b1000000000000001;
(short)0b1000000000000001;
(short)0b1001000000001001;
(short)0b1000100000010001;
(short)0b0100011111100010;
(short)0b0010000000000100;
(short)0b0001000000001000;
(short)0b0000100000010000;
(short)0b0000011111100000;
}
总之，JDK7新增的这种整形的表示方对处理二制的数据操作提供了很好的帮助。
String 可以作为switch的statement，很多编程人员都遇到过通过一个字符串来决定程序流转的问题，以JDK7以前大家得通过一些特殊的处理才能得以实现。如先通过一个转换器将
字符串转换为数字类型。JDK7就不需要做那些转换可以直接将字符串做条件来使用。如下：
public String getTypeOfDayWithSwitchStatement(String dayOfWeekArg) {
String typeOfDay;
switch (dayOfWeekArg) {
case "Monday":
typeOfDay = "Start of work week";
break;
case "Tuesday":
case "Wednesday":
case "Thursday":
typeOfDay = "Midweek";
break;
case "Friday":
typeOfDay = "End of work week";
break;
case "Saturday":
case "Sunday":
typeOfDay = "Weekend";
break;
default:
throw new IllegalArgumentException("Invalid day of the week: " + dayOfWeekArg);
}
return typeOfDay;
}
是不是觉得上面的代码很简明？
今天先研究到这里，明天研究JDK7最新的异常处理处理特性.
