type-conversion - java.util.UnknownFormatConversionException：转换='N'

Question

这是我的代码：

package com.example.java;

public class PackageDataTest {

    public static void main(String[] args) {
        PackageData data1 = new PackageData("John Davids");
        System.out.printf("%Number of object created until now is : %d", PackageData.count);
    }
}

class PackageData {

    static int count = 0;
    String name;

    public PackageData(){
        this.name = "";
        ++count;
    }

    public PackageData(String name) {
        this.name = name;
        ++count;
    }

    public int getCount() { return count; }
}

我不断收到以下错误：

“线程“主”java.util.UnknownFormatConversionException 中的异常：转换 = 'N'”

Answer 1

%N 不是有效的转换格式，%n 用于换行。

因此，如果您将代码替换如下：

System.out.printf("%nNumber of object created until now is : %d", PackageData.count); 

输出将在新行上：

Number of object created until now is : 1

查看此讨论：printf 中 Java 的“%n”是怎么回事？