为什么样例可以过，结果：

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RE #1 Runtime Error. Program exited with code 1. 0ms/0B

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RE #2 Runtime Error. Program exited with code 1. 83ms/27.62MB

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AC #3 Accepted, 得分 20.ok accepted 83ms/27.45MB

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WA #4 Wrong Answer.wrong answer On line 1 column 1, read 0, expected 8. 0ms/0B

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RE #5 Runtime Error. Program exited with code 1.

有没有哪位学JAVA的帮我看一下，我才刚学没多久

import java.util.Scanner;
public class Main {
    public static void main(String[] args){
        Scanner s = new Scanner(System.in);
        int a,b,c;
        a = s.nextInt();
        b = s.nextInt();
        c = s.nextInt();
        float i = P(a,b,c);
        float x = (float) S(i,a,b,c);
        String str = String.format("%.1f",x);
        System.out.println(str);
    }
    static int P(int a,int b,int c){
        return ((a + b + c)) / 2;
    }
    static double S(float i, int a, int b, int c){
        float sjx = i * (i - a) * (i - b) * (i - c);
        return sqrt(sjx);
    }
    public static double sqrt(double c){
        if(c < 0) return Double.NaN;
        double err = 1e-7;
        double x = c;
        while(Math.abs(x - c/x) > err){
            x = (x + c/x) / 2.0;
        }
        return x;
    }
}