java 问题

[zyp627]

系统提示：无法从静态上下文中引入非静态方法。下面是我的代码，关于各种变量使用到底是怎么回事？在JAVA里是不是必须每个类要建立对象才能调用方法？我的代码问题在那里？

public class TestEx{
public static void main(String[] args){

System.out.println("jia"+" " +Pp.add(8,4));
System.out.println("jian" + " " +Pp.del(8,4));
System.out.println(Pp.cheng(8,4));
System.out.println(Pp.chu(8,4));

System.out.println(Pp.chu(8,0));
}
}

class Pp{


int add(int m,int n){
int x;
x = m + n;
return x;
}
int del(int a,int b){
int y;
y = a + b;
return y;
}
int cheng(int c, int d){
int t;
t = c*d;
return t;
}
int chu(int x,int y){
int d;
try{ d = x/y;
}catch(ArithmeticException e){
System.out.println("被除数为零，请重新输入！");

}
return d;
}


}

[xujiaxiang]

Pp p = new Pp();
System.out.println("jia"+"  " +p.add(8,4)); 
System.out.println("jian" + "  " +p.del(8,4)); 
System.out.println(p.cheng(8,4)); 
System.out.println(p.chu(8,4)); 

System.out.println(p.chu(8,0)); 
} 

改这里

[爱摸鱼de老邪]

public class TestEx{
public static void main(String[] args){

System.out.println("jia"+"  " +Pp.add(8,4));
System.out.println("jian" + "  " +Pp.del(8,4));
System.out.println(Pp.cheng(8,4));
System.out.println(Pp.chu(8,4));

System.out.println(Pp.chu(8,0));
}
}

class Pp{


static int add(int m,int n){
int x;
x = m + n;
return x;
}
static int del(int a,int b){
int y;
y = a + b;
return y;
}
static int cheng(int c, int d){
int t;
t = c*d;
return t;
}
static int chu(int x,int y){
int d;
  try{ d = x/y;
  }catch(ArithmeticException e){
            System.out.println("被除数为零，请重新输入！");
 
  }
  return d;
}


}