Java数组常用API
java.util.Arrays Arrays.asList() 数组转换成列表 String[] strArray = {"zhang", "xue", "zhi"}; List<String> list = Arrays.asList(strArray); // 打印元素 for (int i=0; i<list.size(); i++) { System.out.print(list.get(i) + " "); } 1 2 3 4 5 6 Arrays.binarySearch() 二分查找 查找前,一定要排序。 如果查找元素不存在,返回(-(insertion point) - 1)。 自然数表示查到,负数表示没有查找。 int[] a = {3,5,9,7,2}; Arrays.sort(a); // 排序 // 打印数组 for (int item : a) System.out.print(item + " "); System.out.println(); // 二分查找 int ind1 = Arrays.binarySearch(a, 2); int ind2 = Arrays.binarySearch(a, 4); int ind3 = Arrays.binarySearch(a, 1, 3, 5); System.out.println("2的查找位置:" + ind1); System.out.println("4的查找位置:" + ind2); System.out.println("5的查找位置:" + ind3); // 字符串 String[] strArray = {"aa", "bc", "ab", "cd"}; Arrays.sort(strArray); int ind4 = Arrays.binarySearch(strArray, "bc"); System.out.println("'bc'的查找位置是:" + ind4); 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Arrays.copyOf() 复制长度大于原数组长度时,后面补零。 int[] a = {3,5,9,7,2}; int[] newa = Arrays.copyOf(a, 2); int[] newa2 = Arrays.copyOf(a, 7); //复制长度大于原数组的长度 for (int item : newa) System.out.print(item + " "); System.out.println(); for (int item : newa2) System.out.print(item + " "); System.out.println(); 1 2 3 4 5 6 7 8 9 10 11 Arrays.copyOfRange() 复制长度大于原数组长度时,后面补零。 Java中区间一般都是左闭右开[a,b),即包括左边,不包括右边。 int[] a = {3,5,9,7,2}; int[] newa = Arrays.copyOfRange(a, 1, 3); int[] newa2 = Arrays.copyOfRange(a, 1, 8); //复制长度大于原数组的长度 for (int item : newa) System.out.print(item + " "); System.out.println(); for (int item : newa2) System.out.print(item + " "); System.out.println(); 1 2 3 4 5 6 7 8 9 10 11 Arrays.deepEquals() 比较数组元素是否深层相等。 一维数组无区别,高维数组有区别。 String[][] ticTacToe1 = { { " O ", " O ", " X " }, { " O ", " X ", " X " },{ " X ", " O ", " O " } }; String[][] ticTacToe2 = { { " O ", " O ", " X " }, { " O ", " X ", " X " },{ " X ", " O ", " O " } }; System.out.println(Arrays.equals(ticTacToe1, ticTacToe2));// false System.out.println(Arrays.deepEquals(ticTacToe1, ticTacToe2));// true String[] ticTacToe3 = { " O ", " O ", " X " }; String[] ticTacToe4 = { " O ", " O ", " X " }; System.out.println(Arrays.equals(ticTacToe3, ticTacToe4)); // true System.out.println(Arrays.deepEquals(ticTacToe3, ticTacToe4)); // true 1 2 3 4 5 6 7 8 9 Arrays.deepHashCode() 深层相等的两个数组的深层哈希编码也相等。 String[][] ticTacToe1 = { { " O ", " O ", " X " }, { " O ", " X ", " X " },{ " X ", " O ", " O " } }; String[][] ticTacToe2 = { { " O ", " O ", " X " }, { " O ", " X ", " X " },{ " X ", " O ", " O " } }; System.out.println(Arrays.equals(ticTacToe1, ticTacToe2));// false System.out.println(Arrays.deepEquals(ticTacToe1, ticTacToe2));// true // ticTacToe1和ticTacToe1深层相等,深层哈希编码也相等。 System.out.println(Arrays.deepHashCode(ticTacToe1)); System.out.println(Arrays.deepHashCode(ticTacToe2)); 1 2 3 4 5 6 7 Arrays.deepToString() // 二维数组有区别 String[][] ticTacToe1 = { { " O ", " O ", " X " }, { " O ", " X ", " X " },{ " X ", " O ", " O " } }; System.out.println(Arrays.deepToString(ticTacToe1)); // 深层变换成字符串 System.out.println(Arrays.toString(ticTacToe1)); // 一般 // 一维数组无区别 String[] ticTacToe3 = { " O ", " O ", " X " }; System.out.println(Arrays.deepToString(ticTacToe3)); // 深层变换成字符串 System.out.println(Arrays.toString(ticTacToe3)); // 一般 1 2 3 4 5 6 7 8 9 Arrays.equals() 参考Arrays.deepArrays() Arrays.fill() 填充数组元素 int[] a = {1,2,3,4,5,6}; Arrays.fill(a, 8);//全部填充 for (int item : a) System.out.print(item + " "); System.out.println(); Arrays.fill(a, 1, 3, 0);//指定范围,替换 for (int item : a) System.out.print(item + " "); 1 2 3 4 5 6 7 8 9 10 Arrays.hashCode() 如果两个数组相等,哈希编码也相等。 int[] a = {1,2,3,4,5,6}; int[] b = {1,2,3,4,5,6}; String[] c = {"a", "b", "c"}; String[] d = {"a", "b", "c"}; System.out.println("a==b:" + Arrays.equals(a, b)); System.out.println("a和b的哈希码分别为:" + Arrays.hashCode(a) + "\t" + Arrays.hashCode(b)); // 字符串 System.out.println("c==d:" + Arrays.equals(c, d)); System.out.println("c和d的哈希码分别为:" + Arrays.hashCode(c) + "\t" + Arrays.hashCode(d)); System.out.println("c==d:" + c.equals(d)); System.out.println("c和d的哈希码分别为:" + c.hashCode() + "\t" + d.hashCode()); 1 2 3 4 5 6 7 8 9 10 11 12 13 Arrays.sort() int[] a = {6,5,4,3,2,1}; // 指定范围排序 Arrays.sort(a, 1, 4); for (int item : a) System.out.print(item + " "); System.out.println(); // 全部元素排序 Arrays.sort(a); for (int item : a) System.out.print(item + " "); System.out.println(); 1 2 3 4 5 6 7 8 9 10 11 Arrays.toString() 参考 Arrays.deepToString() 遍历数组 遍历一维数组 int[] a = {6,5,4,3,2,1}; // 遍历数组 for for (int i=0; i<a.length; i++) if (i == a.length-1) System.out.print(a[i]); else System.out.print(a[i] + ", "); System.out.println(); // 遍历数组 - foreach for (int item : a) if (item == a[a.length-1]) System.out.print(item); else System.out.print(item + ", "); 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 遍历二维数组 int[][] a = {{1,2,3}, {4,5,6}, {7,8,9}}; // 遍历二维数组 for for (int i=0; i<a.length; i++) { for (int j=0; j<a[i].length; j++) if (j == a[i].length-1) System.out.print(a[i][j]); else System.out.print(a[i][j] + ", "); System.out.println(); } 1 2 3 4 5 6 7 8 9 10 数组对象的方法 数组从java.lang.Object继承的方法:clone, equals, finalize, getClass, hashCode, notify, toString, wait arr.clone() 通过克隆生成另一个数组 int[] a = {1,2,3,4,5,6}; int[] b = a.clone(); Arrays.fill(a, 1, 4, 0); // 改变a,看是否对b有影响 //打印b for (int item : b) System.out.print(item + " "); 1 2 3 4 5 6 arr.equals() arr.equals()和Arrays.equals()不同 int[] a = {1,2,3,4,5,6}; int[] b = a.clone(); int[] c = a; // 判等 System.out.println(Arrays.equals(a, b)); // 比较内容 System.out.println(a.equals(b)); //比较地址 System.out.println(a.equals(c)); 1 2 3 4 5 6 7 arr.getClass() int[] a = {1,2,3,4,5,6}; System.out.println(a.getClass()); 1 2 3 arr.hashCode() int[] a = {1,2,3,4,5,6}; // 两种方法的结果不同。 System.out.println(a.hashCode()); System.out.println(Arrays.hashCode(a)); // Arrays.hashCode() 1 2 3 4 5 arr.toString() int[] a = {1,2,3,4,5,6}; System.out.println(a.toString()); // 地址 System.out.println(Arrays.toString(a)); //字符串 1 2 3 4 数组对象的属性 arr.length int[] a = {1,2,3,4,5,6}; int len = a.length; System.out.println(len);
转自:https://blog.csdn.net/xuezhisdc/article/details/52346800
参考:https://blog.csdn.net/qq_19558705/article/details/50436583