App2_1.java
//filename:App2_1.java
public class App2_1
{
public static void main(String[] args)
{
System.out.println("Hello java !");
}
}

App3_4.java
//filename:App3_4.java
import java.io.*;
public class App3_4
{
public static void main(String[] args) throws IOException
{
float num;
String str;
BufferedReader buf;
buf=new BufferedReader(new InputStreamReader(System.in));
System.out.print("请输入一个实数：");
str=buf.readLine();
num=Float.parseFloat(str);
System.out.println("您输入的数为："+num);
}
}

p62_8
//filename P62_8.java
import java.util.*;
public class P62_8
{
public static void main(String[] args)
{
int n,sum=0,i=0;
Scanner buf=new Scanner(System.in);
n=buf.nextInt();
for(i=n;i>0;i=i/10)
{
sum=sum+(i%10);
}
System.out.println("各位数数字和为"+sum);
}
}

//filename:P62_5.java
import java.util.*;
public class P62_5{
public static void main(String[] args)
{
double h=0,sum=0,jie=1,i=2,n=1,j=1;
Scanner buf=new Scanner(System.in);
n=buf.nextInt();
if(n%2==0)
for(i=2;i<=n;i=i+2)
{
for(j=1;j<=i;j++)
{
jie=jie*j;
}
h=(i-1)/jie;
sum=sum+h;
jie=1;
}
else
{
for(i=2;i<=n;i=i+2)
{
for(j=1;j<=i;j++)
{
jie=jie*j;
}
h=(i-1)/jie;
sum=sum+h;
jie=1;
}
for(j=1;j<=n;j++)
{
jie=jie*j;
}
sum=sum+(1/jie);
}
System.out.println("结果为"+sum);
}
}

//filename:P95_13.java
import java.util.*;
class Student
{
String id,name,sex,leader;
double Math,Chinese,English;
void shuru()
{
Scanner buf=new Scanner(System.in);
Math=buf.nextInt();
Scanner buf1=new Scanner(System.in);
Chinese=buf1.nextInt();
Scanner buf2=new Scanner(System.in);
English=buf2.nextInt();
}
double zongfen()
{
return (Math+Chinese+English);
}
double pingjun()
{
return (Math+Chinese+English)/3;
}
}
public class P95_13
{
public static void main(String[] args)
{
Student stu;
stu=new Student();
stu.id="01";
stu.name="张三";
stu.sex="男";
stu.leader="是";
stu.shuru();
System.out.println("学号="+stu.id+" 姓名="+stu.name+" 性别="+stu.sex+" 班干部否="+stu.leader);
System.out.println("数学="+stu.Math+" 语文="+stu.Chinese+" 英语="+stu.English+" 总分="+stu.zongfen()+"平均分="+stu.pingjun());
}
}

//filename:App7_4.java
class Cylinder
{
private double radius;
private int height;
private double pi=3.14;
public Cylinder(double r,int h)
{
radius=r;
height=h;
}
double area()
{
return pi*radius*radius;
}
double volume()
{
return area()*height;
}
}
public class App7_4
{
public static void main(String[] args)
{
Cylinder volu=new Cylinder(3.5,8);
System.out.println("圆柱底面积="+volu.area());
System.out.println("圆柱体体积="+volu.volume());
}
}

//filename:App7_5.java
class Cylinder
{
private double radius;
private int height;
private double pi=3.14;
String color;
public Cylinder()
{
radius=1;
height=2;
color="绿色";
}
public Cylinder(double r,int h,String str)
{
radius=r;
height=h;
color=str;
}
public void setColor()
{
System.out.println("该圆柱颜色为："+color);
}
double area()
{
return pi*radius*radius;
}
double volume()
{
return area()*height;
}
}
public class App7_5
{
public static void main(String[] args)
{
Cylinder volu1=new Cylinder();
System.out.println("圆柱1底面积="+volu1.area());
System.out.println("圆柱1体积="+volu1.volume());
volu1.setColor();
Cylinder volu2=new Cylinder(2.5,8,"红色");
System.out.println("圆柱1底面积="+volu2.area());
System.out.println("圆柱2体积="+volu2.volume());
volu2.setColor();
}
}

//filename:App7_6.java
class Cylinder
{
private double radius;
private int height;
private double pi=3.14;
String color;
public Cylinder()
{
this(2.5, 5, "红色");
System.out.println("无参构造方法被调用了");
}
public Cylinder(double r, int h, String str)
{
System.out.println("有参构造方法被调用了");
radius=r;
height=h;
color=str;
}
public void show()
{
System.out.println("圆柱底半径为:"+ radius);
System.out.println("圆柱体的高为:"+ height);
System.out.println("圆柱的颜色为:"+color);
}
double area()
{
return pi*radius*radius;
}
double volume()
{
return area()*height;
}
}
public class App7_6
{
public static void main(String[] args)
{
Cylinder volu=new Cylinder();
System.out.println("圆柱底面积="+ volu.area());
System.out.println("圆柱体体积="+ volu.volume());
volu.show();
}
}

//filename:App7_7.java
class Cylinder
{
private double radius;
private int height;
private double pi=3.14;
String color;
private Cylinder()
{
System.out.println("无参构造方法被调用了");
}
public Cylinder(double r,int h, String str)
{
this();
radius=r;
height=h;
color=str;
}
public void show()
{
System.out.println("圆柱底半径为："+ radius);
System.out.println("圆柱体的高为："+ height);
System.out.println("圆柱的颜色为："+ color);
}
double area()
{
return pi*radius*radius;
}
double volume()
{
return area()*height;
}}
public class App7_7
{
public static void main(String[] args)
{
Cylinder volu=new Cylinder(2.5,5,"蓝色");
System.out.println("圆柱底面积="+volu.area());
System.out.println("圆柱体体积="+volu.volume());
volu.show();
}}

//filename:App7_8.java
class Cylinder
{
private static int num=0;
private static double pi=3.14;
private double radius;
private int height;
public Cylinder(double r,int h)
{
radius=r;
height=h;
num++;
}
public void count()
{
System.out.print("创建了"+num+"个对象:");
}
double area()
{
return pi*radius*radius;
}
double volume()
{
return area()*height;
}}
public class App7_8
{
public static void main(String[] arge)
{
Cylinder volu1=new Cylinder(2.5,5);
volu1.count();
System.out.println("圆柱1的体积="+volu1.volume());
Cylinder volu2=new Cylinder(1.0,2);
volu2.count();
System.out.println("圆柱2的体积="+volu2.volume());
}}

//filename:App7_9.java
class Cylinder
{
private static int num=0;
private static double pi=3.14;
private double radius;
private int height;
public Cylinder(double r,int h)
{
radius=r;
height=h;
num++;
}
public static void count()
{
System.out.println("创建了"+num+"个对象");
}
double area()
{
return pi*radius*radius;
}
double volume()
{
return area()*height;
}}
public class App7_9
{
public static void main(String[] args)
{
Cylinder.count();
Cylinder volu1=new Cylinder(2.5,3);
volu1.count();
System.out.println("圆柱1的体积"+volu1.volume());
Cylinder volu2=new Cylinder(1.0,2);
Cylinder.count();
System.out.println("圆柱2的体积"+volu2.volume());
}
}

//filename:App7_10.java
class Cylinder
{
private static double pi=3.14;
private double radius;
private int height;
public Cylinder(double r,int h)
{
radius=r;
height=h;
}
public void setCylinder(double r,int h)
{
radius=r;
height=h;
}
double volume()
{
return pi*radius*radius*height;
}
}
public class App7_10
{
public static void main(String[] args)
{
Cylinder volu1,volu2;
volu1=new Cylinder(2.5,5);
System.out.println("圆柱1的体积="+volu1.volume());
volu2=volu1;
volu2.setCylinder(1.0,2);
System.out.println("圆柱2的体积="+volu1.volume());
}}

//filename:App7_11.java
class Cylinder
{
private static double pi=3.14;
private double radius;
private int height;
public Cylinder(double r,int h)
{
radius=r;
height=h;
}
public void compare(Cylinder volu)
{
if(this==volu)
System.out.println("这两个对象相等");
else
System.out.println("这两个对象不相等");
}}
public class App7_11
{
public static void main(String[] args)
{
Cylinder volu1=new Cylinder(1.0,2);
Cylinder volu2=new Cylinder(1.0,2);
Cylinder volu3=volu1;
volu1.compare(volu2);
volu1.compare(volu3);
}}

//filename:App8_3.java
class Person
{
protected String name;
protected int age;
public Person() {}
public Person(String name ,int age)
{
this.name=name;
this.age=age;
}
protected void show()
{
System.out.println("姓名:"+name+" 年龄:"+age);
}
}
class Student extends Person
{
private String department;
int age=20;
public Student(String xm,String dep)
{
name=xm;
department=dep;
super.age=25;
System.out.println("子类 Student中的成员变量age="+age);
super.show();
System.out.println("系别："+department);
}
}
public class App8_3
{
public static void main(String[] args)
{
Student stu=new Student("李小四","信息系");
}
}