View Compilation Error

0_0_2342676_15556\Main.java:2: 需要 '{'
public class main(){
                 ^
0_0_2342676_15556\Main.java:4: 需要 ')'
    String srta = JOptionPane.showInputDialog(null,a:);
                                                    ^
0_0_2342676_15556\Main.java:4: 非法的表达式开始
    String srta = JOptionPane.showInputDialog(null,a:);
                                                     ^
0_0_2342676_15556\Main.java:5: 需要 ')'
    String srtb = JOptionPane.showInputDialog(null,b:);
                                                    ^
0_0_2342676_15556\Main.java:5: 非法的表达式开始
    String srtb = JOptionPane.showInputDialog(null,b:);
                                                     ^
5 错误