if (条件表达式) 
{
    语句1
}
else 
{
    语句2
}
语句3

if(a>5) b=1
else if(a>4) b=2
else if(a>3) b=3
...
else b=-1;

switch(条件表达式)
{
case 常量表达式1:
     语句1 ;
     break ;

case 常量表达式2:
     语句2 ;
     break ;
//......
case 常量表达式n:
     语句n ;
     break ;
default:
     //
     break
}

class switch test

public static void main(string args[])
throws java.io.ioexception

char a;
system.out.println("enter a number from 1--3:");
a=(char)system.in.read();
switch(a)

case'1':system.out.println("win a car!");break;
case'2':system.out.println("picked the goat");break
case'3':system.out.println("get to keep your 100");
break;
default:system.out.println("entry");

class switchtest

public static void main (string args[])
throws java.io.ioexception

int numberofdigits=0,numberofspaces=0,numberofothers=0;
char c;
while((c=(char)system.in.read())!='')

switch(c)

case'0':
case'1':
...
...
case'8':
case'9':numberofdigits++;break;
case' ':numberofspaces++;break;
default:numberofothers++;break;

system.out.println(":");
system.out.println("number of digits="+numberofdigits+"");
system.out.println("number of spaces="+numberofspaces+"");
system.out.println("number of others="+numberofothers+"");