aa没有初始化 float aa=0;
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import java.io.*;public class emp309{public static void main(String args[]){
float aa=0;String s;try {System.out.print("Please input a float:");BufferedReader br=new BufferedReader(new InputStreamReader(System.in));s=br.readLine(); aa=Float.parseFloat(s);
}catch(IOException e) {}System.out.println(aa);}}
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import java.io.*;public class emp309{public static void main(String args[]){
float aa=0;String s;try {System.out.print("Please input a float:");BufferedReader br=new BufferedReader(new InputStreamReader(System.in));s=br.readLine(); aa=Float.parseFloat(s);
}catch(IOException e) {}System.out.println(aa);}}
String s;
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float aa=0;
String s=null;