1.基本格式书写格式public class Data_Lisr { int grades; public Data_Lisr(){ System.out.println(调用了无参数构造器grades); } public Data_Lisr(int grades){ System.out.println(调用了有参数构造器this.grades); } }调用格式static void main() { //无参数构造器 Data_Lisr sr new Data_Lisr(); //有参数构造器 Data_Lisr sr new Data_Lisr(123); }