Java Lambda mapToDouble 精度问题

原创已于 2022-03-11 12:02:58 修改 · 4.4w 阅读

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于 2016-11-08 08:53:26 首次发布

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Java Lambda mapToDouble 精度问题

public class Menu {
	
	/**
	 * 菜品名称
	 */
	private String name;
	/**
	 * 菜品单价
	 */
	private Double price;
	/**
	 * 菜品斤数
	 */
	private Double kilo;
	/**
	 * 菜品类型：蔬菜、水果、肉类
	 */
	private String type;
	
	public Menu() {
		
	}

	public Menu(String name, Double price, Double kilo, String type) {
		super();
		this.name = name;
		this.price = price;
		this.kilo = kilo;
		this.type = type;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public Double getPrice() {
		return price;
	}

	public void setPrice(Double price) {
		this.price = price;
	}

	public Double getKilo() {
		return kilo;
	}

	public void setKilo(Double kilo) {
		this.kilo = kilo;
	}

	public String getType() {
		return type;
	}

	public void setType(String type) {
		this.type = type;
	}
	
	
}

Menu pork    = new Menu("猪肉", 9.9, 10.0, "肉类");
Menu beef    = new Menu("牛肉", 38.8, 5.0, "肉类");
Menu chicken = new Menu("鸡肉", 6.5, 30.0, "肉类");
Menu tomato  = new Menu("土豆", 3.5, 30.0, "蔬菜");
Menu potato  = new Menu("西红柿", 7.5, 20.0, "蔬菜");
Menu apple   = new Menu("苹果", 3.5, 20.0, "水果");
Menu orange  = new Menu("橙子", 4.0, 20.0, "水果");
List<Menu> menuList = Arrays.asList(pork, beef, chicken, tomato, potato, apple, orange);

double sum = menuList.stream().mapToDouble(Menu::getPrice).sum();
System.out.println(sum);

73.69999999999999

DecimalFormat df = new DecimalFormat();
df.setRoundingMode(RoundingMode.HALF_UP);

double sum = menuList.stream().mapToDouble(Menu::getPrice).sum();
System.out.println(df.format(sum));