布尔值未使用构造函数初始化

Question

I created a simple system to create a Hamburger, where you can add ingredients and then calculate the price with the ingredients you picked, the base price is 5 without extra ingredients and for each ingredient you want more, I set it's value to true and I have a price counter that will add 1 more euro/dollar to the base price, the problem here is that the boolean fields aren't being initiated as false, even tho I set it in the class Constructor, I can't understand why.

I tried setting the boolean fields to false because they're not in the parameters but they won't change, in the code I provided I want the price to be 5 because I haven't yet set any other ingredients so the the method price() should only return the base price I set(5) and not add any other ingredients, but that doesn't happen because all boolean fields are set to true meaning that they'll add 1 to each true value, so the returned price will be 9. This is probably really stupid to ask but I'm a total programming noob so I would thank if someone would explain why am I not obtaining the result I want.

public class Hamburger {
    private String bun;
    private String meat;
    private double price;
    private boolean letuce;
    private boolean tomato;
    private boolean bacon;
    private boolean sauce;

    public Hamburger(String bun, String meat) {
        this.bun = bun;
        this.meat = meat;
        this.price = 5;
        this.letuce = false;
        this.tomato = false;
        this.bacon = false;
        this.sauce = false;
    }

    public double price() {

        if(letuce = true)
            price+=1;
        if(tomato = true)
            price+=1;
        if(bacon = true)
            price+=1;
        if(sauce = true)
            price+=1;

        return price;           
    }

    public void setLetuce(boolean letuce) {
        this.letuce = letuce;
    }
    public void setTomato(boolean tomato) {
        this.tomato = tomato;
    }
    public void setBacon(boolean bacon) {
        this.bacon = bacon;
    }
    public void setSauce(boolean sauce) {
        this.sauce = sauce;
    }
}

I expect the output of 5 but the output is 9

Answer 1

Inside your if checks you use = instead of == . The single = is an assignment and an assignment returns the value assigned, in this case true that's why your code returns 9 instead of 5 This will work as you expected:

public double price() {

    if(letuce == true)
        price+=1;
    if(tomato == true)
        price+=1;
    if(bacon == true)
        price+=1;
    if(sauce == true)
        price+=1;

    return price;           
}

Answer 2

letuce = true

是一个赋值，将letuce的值更改为true，并且本身具有true的值