打印 Java 数组的最简单方法是什么？

What's the simplest way to print a Java array?

提问by Alex Spurling

In Java, arrays don't override toString(), so if you try to print one directly, you get the className+ '@' + the hex of the hashCodeof the array, as defined by Object.toString():

在 Java 中，数组不会覆盖toString()，所以如果你尝试直接打印一个，你会得到className+ '@' +hashCode数组的十六进制，定义如下Object.toString()：

int[] intArray = new int[] {1, 2, 3, 4, 5};
System.out.println(intArray);     // prints something like '[I@3343c8b3'

But usually, we'd actually want something more like [1, 2, 3, 4, 5]. What's the simplest way of doing that? Here are some example inputs and outputs:

但通常，我们实际上想要更像[1, 2, 3, 4, 5]. 最简单的方法是什么？以下是一些示例输入和输出：

// Array of primitives:
int[] intArray = new int[] {1, 2, 3, 4, 5};
//output: [1, 2, 3, 4, 5]

// Array of object references:
String[] strArray = new String[] {"John", "Mary", "Bob"};
//output: [John, Mary, Bob]

采纳答案by Esko

Since Java 5 you can use Arrays.toString(arr)or Arrays.deepToString(arr)for arrays within arrays. Note that the Object[]version calls .toString()on each object in the array. The output is even decorated in the exact way you're asking.

从 Java 5 开始，您可以在数组中使用Arrays.toString(arr)或Arrays.deepToString(arr)数组。请注意，Object[]版本调用.toString()数组中的每个对象。输出甚至以您要求的确切方式进行装饰。

Examples:

例子：

• Simple Array:

  String[] array = new String[] {"John", "Mary", "Bob"};
  System.out.println(Arrays.toString(array));
  

  Output:

  [John, Mary, Bob]
  

• Nested Array:

  String[][] deepArray = new String[][] {{"John", "Mary"}, {"Alice", "Bob"}};
  System.out.println(Arrays.toString(deepArray));
  //output: [[Ljava.lang.String;@106d69c, [Ljava.lang.String;@52e922]
  System.out.println(Arrays.deepToString(deepArray));
  

  Output:

  [[John, Mary], [Alice, Bob]]
  

• doubleArray:

  double[] doubleArray = { 7.0, 9.0, 5.0, 1.0, 3.0 };
  System.out.println(Arrays.toString(doubleArray));
  

  Output:

  [7.0, 9.0, 5.0, 1.0, 3.0 ]
  

• intArray:

  int[] intArray = { 7, 9, 5, 1, 3 };
  System.out.println(Arrays.toString(intArray));
  

  Output:

  [7, 9, 5, 1, 3 ]
  

• 简单数组：

  String[] array = new String[] {"John", "Mary", "Bob"};
  System.out.println(Arrays.toString(array));
  

  输出：

  [John, Mary, Bob]
  

• 嵌套数组：

  String[][] deepArray = new String[][] {{"John", "Mary"}, {"Alice", "Bob"}};
  System.out.println(Arrays.toString(deepArray));
  //output: [[Ljava.lang.String;@106d69c, [Ljava.lang.String;@52e922]
  System.out.println(Arrays.deepToString(deepArray));
  

  输出：

  [[John, Mary], [Alice, Bob]]
  

• double大批：

  double[] doubleArray = { 7.0, 9.0, 5.0, 1.0, 3.0 };
  System.out.println(Arrays.toString(doubleArray));
  

  输出：

  [7.0, 9.0, 5.0, 1.0, 3.0 ]
  

• int大批：

  int[] intArray = { 7, 9, 5, 1, 3 };
  System.out.println(Arrays.toString(intArray));
  

  输出：

  [7, 9, 5, 1, 3 ]
  

回答by Limbic System

Always check the standard libraries first.

总是先检查标准库。

import java.util.Arrays;

Then try:

然后尝试：

System.out.println(Arrays.toString(array));

or if your array contains other arrays as elements:

或者如果您的数组包含其他数组作为元素：

System.out.println(Arrays.deepToString(array));

回答by Ross

If you're using Java 1.4, you can instead do:

如果您使用的是 Java 1.4，则可以改为：

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

(This works in 1.5+ too, of course.)

（当然，这也适用于 1.5+。）

回答by Russ Bateman

This is nice to know, however, as for "always check the standard libraries first" I'd never have stumbled upon the trick of Arrays.toString( myarray )

很高兴知道，但是，至于“始终首先检查标准库”，我从来没有偶然发现 Arrays.toString( myarray )

--since I was concentrating on the type of myarray to see how to do this. I didn't want to have to iterate through the thing: I wanted an easy call to make it come out similar to what I see in the Eclipse debugger and myarray.toString() just wasn't doing it.

--因为我专注于 myarray 的类型以了解如何执行此操作。我不想遍历整个事情：我想要一个简单的调用，使它与我在 Eclipse 调试器中看到的相似，而 myarray.toString() 只是没有这样做。

import java.util.Arrays;
.
.
.
System.out.println( Arrays.toString( myarray ) );

回答by somedude

for(int n: someArray) {
    System.out.println(n+" ");
}

回答by Rhyous

Arrays.deepToString(arr)only prints on one line.

Arrays.deepToString(arr)只打印在一行上。

int[][] table = new int[2][2];

To actually get a table to print as a two dimensional table, I had to do this:

要真正将表格打印为二维表格，我必须这样做：

System.out.println(Arrays.deepToString(table).replaceAll("],", "]," + System.getProperty("line.separator")));

It seems like the Arrays.deepToString(arr)method should take a separator string, but unfortunately it doesn't.

该Arrays.deepToString(arr)方法似乎应该采用分隔符字符串，但不幸的是它没有。

回答by Andrew_Dublin

Using regular forloop is the simplest way of printing array in my opinion. Here you have a sample code based on your intArray

在我看来，使用常规for循环是打印数组的最简单方法。这里有一个基于 intArray 的示例代码

for (int i = 0; i < intArray.length; i++) {
   System.out.print(intArray[i] + ", ");
}

It gives output as yours 1, 2, 3, 4, 5

它给你的输出 1, 2, 3, 4, 5

回答by Eric Baker

In JDK1.8 you can use aggregate operations and a lambda expression:

在 JDK1.8 中，您可以使用聚合操作和 lambda 表达式：

String[] strArray = new String[] {"John", "Mary", "Bob"};

// #1
Arrays.asList(strArray).stream().forEach(s -> System.out.println(s));

// #2
Stream.of(strArray).forEach(System.out::println);

// #3
Arrays.stream(strArray).forEach(System.out::println);

/* output:
John
Mary
Bob
*/

回答by Jean Logeart

To add to all the answers, printing the object as a JSON string is also an option.

要添加到所有答案中，将对象打印为 JSON 字符串也是一种选择。

Using Hymanson:

使用Hyman逊：

ObjectWriter ow = new ObjectMapper().writer().withDefaultPrettyPrinter();
System.out.println(ow.writeValueAsString(anyArray));

Using Gson:

使用 Gson：

Gson gson = new Gson();
System.out.println(gson.toJson(anyArray));

回答by Roam

There's one additional way if your array is of type char[]:

如果您的数组是 char[] 类型，还有一种方法：

char A[] = {'a', 'b', 'c'}; 

System.out.println(A); // no other arguments

prints

印刷

abc