public class BreakInSwitch {
    public int days(int year, int month) {
    	int days = 0;
    	switch (month) {
    	case 1:
    	case 3:
    	case 5:
    	case 7:
    	case 8:
    	case 10:
    	case 12:
    	    days = 31;
    	    break;
    	case 4:
    	case 6:
    	case 9:
    	case 11:
    	    days = 30;
    	    break;
    	case 2:
    		if (year % 4 ==0 && year % 100 != 0 || year % 400 == 0) {
    			days = 29;
    		} else {
    			days = 2;
    		}
    	    break;
    	}
    	return days;
    }
}



import javax.swing.JOptionPane;
public class BreakDemo1 {
    public static void main(String[] args) {
    	BreakInSwitch ob = new BreakInSwitch();
    	String strYear = JOptionPane.showInputDialog("请输入一个年份：");
    	String strMonth = JOptionPane.showInputDialog("请输入一个月份：");
    	int year = Integer.parseInt(strYear);
    	int month = Integer.parseInt(strMonth);
    	int days = ob.days(year, month);
    	JOptionPane.showMessageDialog(null, year + "年" + month + "月有" + days + "天！");
    }
}