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

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():

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:

// 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]

Answer

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.

Examples:

• 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]]
  




• double Array:

  
  
  
  

  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 ]
  




• int Array:

  
  
  
  

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

  
  
  

  Output:

  
  
  

  [7, 9, 5, 1, 3 ]