double a = 1.23;
double b = 5.67;
double c = -0.12;
double d = -7.89;

System.out.println("対象 : " + a);
System.out.println("切り上げ : " + Math.ceil(a));
System.out.println("切り捨て : " + Math.floor(a));
System.out.println("四捨五入 : " + Math.round(a));

System.out.println("対象 : " + b);
System.out.println("切り上げ : " + Math.ceil(b));
System.out.println("切り捨て : " + Math.floor(b));
System.out.println("四捨五入 : " + Math.round(b));

System.out.println("対象 : " + c);
System.out.println("切り上げ : " + Math.ceil(c));
System.out.println("切り捨て : " + Math.floor(c));
System.out.println("四捨五入 : " + Math.round(c));

System.out.println("「" + d + "」に対して");
System.out.println("切り上げ「" + Math.ceil(d) + "」");
System.out.println("切り捨て「" + Math.floor(d) + "」");
System.out.println("四捨五入「" + Math.round(d) + "」");