class PageRankComputer extends AbstractComputer {

    public static final String PAGE_RANK = "page_rank";

    public static final String ALPHA = "alpha";
    public static final double DEFAULT_ALPHA = 0.15D;

    @Override
    public String name() {
        return PAGE_RANK;
    }

    @Override
    public String category() {
        return CATEGORY_RANK;
    }

    @Override
    public void checkParameters(Map<String, Object> parameters) {
        maxSteps(parameters);
        alpha(parameters);
        precision(parameters);
    }

    @Override
    protected Map<String, Object> checkAndCollectParameters(
            Map<String, Object> parameters) {
        return ImmutableMap.of(MAX_STEPS, maxSteps(parameters),
                               ALPHA, alpha(parameters),
                               PRECISION, precision(parameters));
    }

    private static double alpha(Map<String, Object> parameters) {<FILL_FUNCTION_BODY>}
}

        if (!parameters.containsKey(ALPHA)) {
            return DEFAULT_ALPHA;
        }
        double alpha = ParameterUtil.parameterDouble(parameters, ALPHA);
        E.checkArgument(alpha > 0 && alpha < 1,
                        "The value of %s must be (0, 1), but got %s",
                        ALPHA, alpha);
        return alpha;
    
<methods>public non-sealed void <init>() ,public java.lang.Object call(Job<java.lang.Object>, Map<java.lang.String,java.lang.Object>) ,public void checkParameters(Map<java.lang.String,java.lang.Object>) <variables>protected static final java.lang.String CATEGORY_COMM,protected static final java.lang.String CATEGORY_RANK,private static final java.lang.String COMMON,private static final java.lang.String COMPUTER_HOME,public static final long DEFAULT_DEGREE,public static final int DEFAULT_MAX_STEPS,public static final double DEFAULT_PRECISION,public static final int DEFAULT_TIMES,public static final java.lang.String DEGREE,public static final java.lang.String DIRECTION,private static final java.lang.String ENV,private static final java.lang.String EQUAL,private static final java.lang.String HADOOP_HOME,private static final Logger LOG,private static final java.lang.String MAIN_COMMAND,public static final java.lang.String MAX_STEPS,private static final java.lang.String MINUS_C,public static final java.lang.String PRECISION,private static final java.lang.String SPACE,public static final java.lang.String TIMES,private Map<java.lang.String,java.lang.Object> commonConfig,private YAMLConfiguration config