java - 打印Java数组的最简单方法是什么？(What's the simplest way to print a Java array?)

Question

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

(在Java中，数组不会覆盖toString() ，因此，如果尝试直接打印一个，则将得到className +'@'+数组的hashCode的十六进制，如Object.toString()所定义：)

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] .

(但是通常，我们实际上想要的是更多类似[1, 2, 3, 4, 5] 。)

What's the simplest way of doing that?

(最简单的方法是什么？)

Here are some example inputs and outputs:

(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]

  ask by Alex Spurling translate from so

Answer 1

Since Java 5 you can use Arrays.toString(arr) or Arrays.deepToString(arr) for arrays within arrays.

(从Java 5开始，您可以将Arrays.toString(arr)或Arrays.deepToString(arr)用于数组中的数组。)

Note that the Object[] version calls .toString() on each object in the array.

(请注意， Object[]版本在数组中的每个对象上调用.toString() 。)

The output is even decorated in the exact way you're asking.

(输出甚至按照您的要求进行修饰。)

Examples:

(例子：)

• Simple Array: (简单数组：)

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

  Output:

  (输出：)

   [John, Mary, Bob] 

• Nested Array: (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)); 

  Output:

  (输出：)

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

• double Array: (double数组：)

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

  Output:

  (输出：)

   [7.0, 9.0, 5.0, 1.0, 3.0 ] 

• int Array: (int数组：)

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

  Output:

  (输出：)

   [7, 9, 5, 1, 3 ]