-公用类型 CPU必须在它自己的文件中定义 没有为缺省构造函数定义隐式超构造函数Object ()。必须定义显式构造函数void setSpeed (int m)

public class PC {
CPU cpu;//定义cpu为CPU类型
HardDisk HD;
public void setCPU(CPU c){
cpu=c;
}
public void setHardDisk(HardDisk h){
HD=h;
}
public void show() {
System.out.println("cpu的速度："+cpu.getSpeed()+"硬盘的容量："+HD.getAmount());
}

}

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class CPU{
  int m;
  public CPU(){}
  void setSpeed (int m){
    this.m = m;
  }
  public int getSpeed (){
  return this.m;
  }
}