Cannot output formatted double in Java

Here's what I do:

double x = 7.0;开发者_如何学JAVA  
System.out.printf("%.2f", x);

Eclipse gives me this error "The method printf(String, Object[]) in the type PrintStream is not applicable for the arguments (String, double)"

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Are you using a version of Java older than 1.5? Or maybe an older compiler compliance setting in Eclipse? (e.g. 1.4) In fact, I am pretty sure that is the cause - I just switched my compliance setting to 1.4 and I get the same error as you.

Check your Project's Compiler Compliance setting:

• Select the Project
• Right click and choose Properties
• go to 'Java Compiler'
• change your compiler compliance and ensure you are using a JRE of that version or higher

This will work once you are using Java 1.5 or higher, since the printf method was added in 1.5.

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I ran the following and I didn't seem to have this problem. Are you getting an error from Eclipse's code inspection, or from the Java compiler?

public class TestDouble {
  public static void main(String[] args) {
     double x = 7.0;
     System.out.printf("%.2f", x);
  }
}

This will also work and may stop Eclipse from complaining:

public class TestDouble {
  public static void main(String[] args) {
     double x = 7.0;
     System.out.printf("%.2f", new Double(x));
  }
}