Mapreduce 求各个部门最高工资的员工姓名，用java ，不调用get方法

可以使用MapReduce实现该功能，具体实现步骤如下：

1. Map阶段：将输入的员工信息按照部门编号作为key，员工姓名和工资作为value进行映射。

public static class Map extends Mapper<LongWritable, Text, Text, Text> {
    private Text outKey = new Text();
    private Text outValue = new Text();

    @Override
    protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
        String[] fields = value.toString().split(",");
        String deptNo = fields[0];
        String empName = fields[1];
        String salary = fields[2];

        outKey.set(deptNo);
        outValue.set(empName + ":" + salary);
        context.write(outKey, outValue);
    }
}

2. Reduce阶段：对于每个部门，遍历其所有员工的工资，找出最高工资，并将其对应的员工姓名输出。

public static class Reduce extends Reducer<Text, Text, Text, Text> {
    private Text outValue = new Text();

    @Override
    protected void reduce(Text key, Iterable<Text> values, Context context) throws IOException, InterruptedException {
        String maxSalaryEmpName = "";
        int maxSalary = Integer.MIN_VALUE;

        for (Text value : values) {
            String[] fields = value.toString().split(":");
            String empName = fields[0];
            int salary = Integer.parseInt(fields[1]);

            if (salary > maxSalary) {
                maxSalary = salary;
                maxSalaryEmpName = empName;
            }
        }

        outValue.set(maxSalaryEmpName);
        context.write(key, outValue);
    }
}

3. Driver阶段：设置MapReduce的输入路径、输出路径、Mapper、Reducer等信息，并提交作业。

public static void main(String[] args) throws Exception {
    Configuration conf = new Configuration();
    Job job = Job.getInstance(conf, "max salary by department");
    job.setJarByClass(MaxSalaryByDepartment.class);

    job.setMapperClass(Map.class);
    job.setReducerClass(Reduce.class);

    job.setOutputKeyClass(Text.class);
    job.setOutputValueClass(Text.class);

    FileInputFormat.addInputPath(job, new Path(args[0]));
    FileOutputFormat.setOutputPath(job, new Path(args[1]));

    System.exit(job.waitForCompletion(true) ? 0 : 1);
}

这样就可以通过MapReduce求出各个部门最高工资的员工姓名了，而且不需要调用get方法。