Priority-based job scheduling

import java.util.*;

public class Main {
    private static final Scanner IN = new Scanner(System.in).useLocale(Locale.ROOT);

java.util.* imports utility type names such as Scanner, Locale and collections. Main is the public class matching Main.java. The private static final IN field holds one shared Scanner for System.in; final prevents replacing that reference. The scanner uses Locale.ROOT.

    static String text() {
        if (!IN.hasNextLine()) throw new IllegalArgumentException("Incomplete input.");
        String value = IN.nextLine().trim();
        if (value.isEmpty() || value.length() > 200) throw new IllegalArgumentException("Text must have 1–200 characters.");
        return value;
    }

text checks whether a line exists, reads it and removes leading/trailing whitespace. Reject empty text and lengths above 200 by throwing IllegalArgumentException. Otherwise return the string. One field is read per line, so these helpers do not mix nextInt with leftover newlines.

    static int integer(int low, int high) {
        int value = Integer.parseInt(text());
        if (value < low || value > high) throw new IllegalArgumentException("Integer out of range.");
        return value;
    }

Integer.parseInt converts the returned string to int or throws NumberFormatException, a subtype of IllegalArgumentException. Reject values outside the caller’s inclusive low/high limits, then return the accepted integer.

    static double number(double low, double high) {
        double value = Double.parseDouble(text());
        if (!Double.isFinite(value) || value < low || value > high) throw new IllegalArgumentException("Number out of range.");
        return value;
    }

Double.parseDouble reads the string as a double. Double.isFinite rejects NaN and infinities as well as the explicit low/high range check. Return only a finite accepted value; exceptions transfer control to a matching catch block.

    static void money(String label, double value) { System.out.printf(Locale.ROOT, "%s: %.2f%n", label, value); }

money is a formatting helper: %s prints the label, %.2f prints two decimal places, and %n ends the line. Locale.ROOT fixes locale-sensitive formatting. The helper can also display non-currency quantities; it does not change the stored value.

static class Task {
        final int taskId,runTime,priority;
        Task(int id,int time,int priority){taskId=id;runTime=time;this.priority=priority;}
    }

Task keeps ID, runtime and priority as final fields. Its constructor assigns all three from the accepted input.

    static final Comparator<Task> ORDER=Comparator.comparingInt((Task t)->t.priority).reversed().thenComparingInt(t->t.taskId);

comparingInt builds priority order; reversed makes larger priority values come first. thenComparingInt chooses smaller taskId when priorities tie. This avoids relying on an unspecified tie order.

    public static void main(String[] args){
        try{
            int n=integer(0,50);PriorityQueue<Task> tasks=new PriorityQueue<>(ORDER);Set<Integer> ids=new HashSet<>();
            for(int i=0;i<n;i++){int id=integer(1,1000000),time=integer(1,1000000),priority=integer(0,100);if(!ids.add(id))throw new IllegalArgumentException("Duplicate task ID.");tasks.add(new Task(id,time,priority));}

Read 0–50 tasks and give PriorityQueue the comparator. A HashSet detects repeated IDs. Each accepted task enters the queue as an object reference.

            System.out.println("Execution order:");long elapsed=0;
            while(!tasks.isEmpty()){Task task=tasks.remove();elapsed+=task.runTime;System.out.println("Task "+task.taskId+" | priority "+task.priority+" | runTime "+task.runTime+" | finishes "+elapsed);}

Repeated remove takes the highest-ranked available task. Add its runtime to long elapsed and print its simulated completion time. This is a non-preemptive ordering demonstration, not real operating-system process execution.

        }catch(IllegalArgumentException e){System.out.println("Invalid input: "+e.getMessage());}
    }
}

The catch handles IllegalArgumentException, including invalid numeric strings from the helpers, and prints its message. The final braces close main and Main. Java objects become eligible for garbage collection when no live reference needs them; this program does not manually free them.