get set的时候报空指针异常

getset方法

private String flieName;
public String getFlieName() {
return flieName;
}
public void setFlieName(String FlieName) {
this.flieName = FlieName;
}

调用set

`f.setFlieName(UseProcess.intputName());
TestMain.test();`
get的时候报空
`int lastnum = getNum(f.getFlieName());
Exception in thread "main" java.lang.NullPointerException
at java.io.FileInputStream.(FileInputStream.java:138)
at java.io.FileInputStream.(FileInputStream.java:101)
at test.UseProcess.getNum(UseProcess.java:54)
at test.UseProcess.(UseProcess.java:47)
at test.TestMain.test(TestMain.java:8)
at test.TestMain.main(TestMain.java:21)`