java overcomes many traditional security problems java programs connot directly access the hardware or address arbitray memory programs run on a virtual hardware _the java virtual machine programs also run in a constrained environment called sandbox.type safety is one cornerstone of the java language security and the verifier is the key defender in the front line .if this defence breaks (i.e.the code is not verfied or the code can be changed after the verfication )then security can be broken .also,flaws in the language inplementation can open up opportunities for attackers
參考答案:java克服了很多传统的安全问题。java程序不能直接访问硬件资源以及任意的取内存地址。程序运行在java虚拟机虚拟硬件之上以及限制的环境（沙箱）。类型安全是java安全的基石，检验类型是关键字类型保护重中之重。如果这样的保护被打破（如代码没被检验或者是可以在被检验后改变），那么安全性将无从谈起。而语言实现上的瑕疵将给攻击者制造机会。
*翻译不好请见谅！*