Exception in thread “main“ java.util.UnknownFormatConversionException: Conversion = ‘ ‘

完整代码如下：

        byte a;
		int b;
		float c;
		double d;
		Scanner reader = new Scanner(System.in);
		a = reader.nextByte();
		b = reader.nextInt();
		c = reader.nextFloat();
		d = reader.nextDouble();
		System.out.printf(" a = % d, b = % 4 d, c = % 5.2 f, d = % f n",a,b,c,d);

在控制台输入字符后报错

10 20 123.456 3.1111
Exception in thread "main" java.util.UnknownFormatConversionException: Conversion = ' '
	at java.util.Formatter.checkText(Unknown Source)
	at java.util.Formatter.parse(Unknown Source)
	at java.util.Formatter.format(Unknown Source)
	at java.io.PrintStream.format(Unknown Source)
	at java.io.PrintStream.printf(Unknown Source)
	at one.ThirdD.main(ThirdD.java:19)

解决办法就是将第十行删掉重新打，同时去掉了空格，然后就运行出来了……（迷之玄学

System.out.printf("a=%d,b=%4d,c=%5.2f,d=%fn",a,b,c,d);

10 20 123.456 3.1111
输出结果:
a=10,b=  20,c=123.46,d=3.111100

最后

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