Double d = new Double("1234567890.12"); 
System.out.println("d:="+d); 
java.text.NumberFormat nf = java.text.NumberFormat.getInstance(); 
nf.setGroupingUsed(false); 
System.out.println("d:="+nf.format(d));

显示结果是:

d:=1.23456789012E9

d:=1234567890.12