数组的声明、 equals 和 "=="

package com.dengwen3; public class Test { /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub float f1[], f2[]; f1 = new float[] {}; int[] arry = new int[10]; int[] arry2 = new int[] { 1, 2 }; /* * 下面的定义是错误的： int []arry3=new int[2]{1,2}; Cannot define dimension * expressions when an array initializer is provided */ int arry3[], arry4[]; arry3 = new int[] { 1, 2, 3 }; arry4 = new int[] { 4, 5, 6 }; int[] arry5, arry6[]; arry5 = new int[] { 1, 2, 3 }; /* 写成arry6=new int[]{1,2,3};这样是错误的， 这里array6是二位数组 */ arry6 = new int[][] { {}, {}, {} }; /* Integer i = new Integer (42); Long l = new Long (42); Double d = new Double (42.0); Which two expressions evaluate to True? (Choose Two) A. (i ==l) B. (i == d) C. (d == 1l) D. (i.equals (d)) E. (d.equals (i)) F. (i.equals (42)) */ /*“==”两边的类型必须一样，所以A，B，C都不对*/ Integer i = new Integer (42); int ii=42; System.out.println(i==ii); Long l = new Long (42); Double d = new Double (42.0); //System.out.println(i==l);错误，//System.out.println(i==l); //Incompatible operand types Integer and Long //System.out.println(d==l); //System.out.println(i==d); System.out.println(i.equals (d));//false System.out.println(d.equals (i));//false System.out.println(i.equals (42));//true /* * equals()方法 当两边类型相同时，对象所代表的基本类型的值相等，则返回真， 对象类型不同时，即使代表的基本类型的值相等 * */ } }