编写账簿类AccountBook类。类中有三个属性：accountName（String类型）、income（double类型）和outcome（double类型）。要求设置收入、支出访问器方法时收入额、支出额不能为负数。定义通过收入和支出自动计算余额的方法compute。再编写测试类，在测试类中用AccountBook类创建一个账簿对象，设置名称是“张三”，收入30，支出10，并将账户名称“张三”，该账户收入额和支出额及该账户的余额输出到控制台：

public class AccountBookTest {
public static void main(String[] args) {
  // TODO Auto-generated method stub
  AccountBook account = new AccountBook("张三",30,10);
  System.out.println("账户名称：" + account.accountName + "收入额：" + account.income + "支出额：" + account.outcome + "余额：" + account.compute(account.income, account.outcome));
}
}
class AccountBook{
String accountName;
double income;
double outcome;
AccountBook(String accountName,double income,double outcome)
{
  this.accountName = accountName;
  if(income > 0)
  {
   this.income = income;
  }
  else{
   System.out.println("收入不能为负数！");
  }
  if(outcome > 0)
  {
   this.outcome = outcome;
  }
  else{
   System.out.println("支出不能为负数！");
  }
}
public double compute(double income,double outcome)
{
  double balance = 0.0;
  balance = income - outcome;
  return balance;
}
}

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