简介

问题来源于stackoverflow.

在java语言中，数组是无法重写toString。如果直接打印一个数组，则得到className+'@'+ hashCode数组的十六进制。

int[] a = new int[] { 1, 2, 3 };
System.out.println(a.toString());
String[] s = new String[] { "1" };
System.out.println(s.toString());

[I@f5ac9e4

[Ljava.lang.String;@123ef382

这种输出格式不太友好，希望能转换为一种可读方式。例如[1,2,3]

Arrays.toString

int[] a = new int[] { 1, 2, 3 };
System.out.println(Arrays.toString(a));

//结果 [1, 2, 3]

Arrays.deepToString

String[] deepArray = new String[] {"Alice", "Bob"};
System.out.println(Arrays.deepToString(deepArray));

//结果 [Alice, Bob]

Arrays.asList

System.out.println(Arrays.asList(deepArray));

//结果 [Alice, Bob]

java8

String.join

String[] deepArray = new String[] {"Alice", "Bob"};

System.out.println(String.join(",",deepArray)); ;
//结果 Alice,Bob

Collectors.joining

int[] ints = new int[] {1, 2, 3, 4, 5};
System.out.println(IntStream.of(ints).mapToObj(Integer::toString).collect(Collectors.joining(", ")));

// 结果 1, 2, 3, 4, 5

函数方式

Stream.forEach

String[] arrayStr = new String[]{"Java ", "Node " , "Python ", "Ruby"};
Arrays.stream(arrayStr).forEach(System.out::print);

//结果 Java Node Python Ruby

String[][] deepArrayStr = new String[][]{{"mkyong1 ", "mkyong2"}, {" mkyong3 ", "mkyong4"}};
Arrays.stream(deepArrayStr).flatMap(x -> Arrays.stream(x)).forEach(System.out::print);

//结果 mkyong1 mkyong2 mkyong3 mkyong4