内容正文:
例 1-1 DoubleVariableDemo.java
class DoubleVariableDemo{
public static void main(String args[]){
double dRadius=2.0d;
double dArea=Math.PI*dRadius*dRadius;
System.out.println("半径为2的圆的面积:"+dArea);
}
}
例 1-2 BooleanConstantDemo.java
class BooleanConstantDemo{
public static void main(String args[]){
final boolean BFLAG=true;
if(BFLAG)
System.out.println("Always Print Out Me!");
else
System.out.println("Never Print Out Me!");
}
}
例 1-3 DecisionDemo.java
class DecisionDemo{
public static void main(String args[]){
short x=1,y=2,z;
// 错误代码
// z = x + y;
// 正确代码
z=(short)(x+y);
System.out.println(z);
}
}
例 1-4 IntegerConstantDemo . java
class IntegerConstantDemo{
public static void main(String args[]){
final byte nMaxValue_1=100;
final short nMaxValue_2=200;
final int nMaxValue_3=300;
final long nMaxValue_4=400;
System.out.println("整数常量的nMaxValue_1值"+nMaxValue_1);
System.out.println("整数常量的nMaxValue_2值"+nMaxValue_2);
System.out.println("整数常量的nMaxValue_3值"+nMaxValue_3);
System.out.println("整数常量的nMaxValue_4值"+nMaxValue_4);
// nMaxValue_1 = nMaxValue_1 + 1; 不能更改常量的值
}
}
例 1-5 DataConversionDemo.java
class DataConversionDemo{
public static void main(String args[]){
int nOp1=2;
float fOp2=2.25f;
float fResult=nOp1*fOp2;
System.out.println("混合运算结果:"+fResult);
}
}
例 1-6 BasicMath.java
class BasicMath{
public static void main(String args[]){
System.out.println("Integer Arithmetic");
int a=1+1;
int b=a*3;
int c=b/4;
int d=c-a;
System.out.println("c = "+c);
System.out.println("d = "+d);
System.out.println("
Floating Point Arithmetic");
double da=1+1;
double db=da*3;
double dc=db/4;
double dd=dc-a;
System.out.println("dc = "+dc);
System.out.println("dd = "+dd);
int x = 42;
double y = 42.25;
System.out.println("x mod 10 = " + x % 10);
System.out.println("y mod 10 = " + y % 10);
}
}
例 1-7 BooleanOperatorDemo.java
class BooleanOperatorDemo{
public static void main(String args[]){
int nOperator1=5;
int nOperator2=10;
if((nO