方法If(boolean)未定义类型

Question

Eclipse不断给我以下错误:

Exception in thread "main" java.lang.Error: Unresolved compilation problems: 
input cannot be resolved
The method If(boolean) is undefined for the type bai1DinhLuatCuLong
Syntax error, insert ";" to complete Statement
F cannot be resolved to a variable

我不明白.我需要修理什么？为什么我不能使用这个If()功能？

我试过浏览Google和Bing,我已经仔细检查了我的Java示例书,但我无法解决这个问题.

import java.util.Scanner;


public class bai1DinhLuatCuLong
{
    public static void main(String[] args)
    { 
    System.out.print("Giá trì c?n tìm (F // q // r) : ");   
    char cantim = input.nextChar();

            // HERE THIS IS WHERE I PUT THE IF STATEMENT !!!
    If (cantim == 'F') {

        Scanner input = new Scanner(System.in); 
        System.out.print("?? l?n c?a ?i?n tích th? nh?t : ");
        double q1 = input.nextDouble();
        System.out.print("?? l?n c?a ?i?n tích th? hai : ");
        double q2 = input.nextDouble();
        System.out.print("Kho?ng cách gi?a 2 ?i?n tích : ");
        double r = input.nextDouble();
        System.out.print("H? s? k s? t? ??ng ???c ??t là 9*10^9 nh? trong h? SI");
        double F = 9 * Math.pow(10,9) * Math.abs(q1) * Math.abs(q2) / Math.pow(r,2);
    }

    System.out.print("?? l?n l?c t??ng tác gi?a 2 ?i?n tích ?i?m : " + "\n L?u ý E là *10");

    }
}

Answer 1

IfI在java 中没有大的上限:它应该是if.

Answer 2

if (cantim == 'F') 它应该很小 i

要么

你需要写一个方法

public boolean If(boolean test)
{
//Your logic.
}

但是,根据您的代码,似乎您正在寻找"if"声明而不是使用新方法.