Modern software engineering practice increasingly brings redundant code into software products, which has caused a phenomenon called bloatware, leading to software system maintenance, performance and reliability issues as well as security problems. With the rapid advances of smart devices and a more connected world, it is never more important to trim bloatware to improve the leanness, agility, reliability, performance, and security of the interconnected software and network systems. Previous methods have limited scopes and are usually not fully automated. In this paper, we propose a new static-analysis-enabled approach to trimming unused code from both Java applications and Java Runtime Environment (JRE) automatically. We have built a tool called JRed on top of the Soot framework. We have conducted a fairly comprehensive evaluation of JRed based on a set of criteria: code size, code complexity, memory footprint, execution and garbage collection time, and security. Our experimental results show that, Java application size can be reduced by 44.5% on average and the JRE code can be reduced by more than 82.5% on average. The code complexity is significantly reduced according to a set of well-known metrics. Furthermore, we report that by trimming redundant code, 48.6% of the known security vulnerabilities in the Java Runtime Environment JRE 6 update 45 has been removed.