Method 1 (Simple Traversal) 

We can use mat.length to find the number of rows in the matrix mat[][]. To find the number of columns in the i-th row, we use mat[i].length.

// Java program to print the elements of
// a 2 D array or matrix
import java.io.*;
class GFG {

	public static void print2D(int mat[][])
	{
		// Loop through all rows
		for (int i = 0; i < mat.length; i++)

			// Loop through all elements of current row
			for (int j = 0; j < mat[i].length; j++)
				System.out.print(mat[i][j] + " ");
	}

	public static void main(String args[])
		throws IOException
	{
		int mat[][] = { { 1, 2, 3, 4 },
						{ 5, 6, 7, 8 },
						{ 9, 10, 11, 12 } };
		print2D(mat);
	}
}

Output

1 2 3 4 5 6 7 8 9 10 11 12 

Method 2 (Using for-each loop) 

This is similar to the above. Instead of simple for loops, we use for each loop here. 

// Java program to print the elements of
// a 2 D array or matrix using for-each
import java.io.*;
class GFG {

	public static void print2D(int mat[][])
	{
		// Loop through all rows
		for (int[] row : mat)

			// Loop through all columns of current row
			for (int x : row)
				System.out.print(x + " ");
	}

	public static void main(String args[])
		throws IOException
	{
		int mat[][] = { { 1, 2, 3, 4 },
						{ 5, 6, 7, 8 },
						{ 9, 10, 11, 12 } };
		print2D(mat);
	}
}

1 2 3 4 5 6 7 8 9 10 11 12 

Method 3 (Prints in matrix style Using Arrays.toString()) 

// Java program to print the elements of
// a 2 D array or matrix using toString()
import java.io.*;
import java.util.*;
class GFG {

	public static void print2D(int mat[][])
	{
		// Loop through all rows
		for (int[] row : mat)

			// converting each row as string
			// and then printing in a separate line
			System.out.println(Arrays.toString(row));
	}

	public static void main(String args[])
		throws IOException
	{
		int mat[][] = { { 1, 2, 3, 4 },
						{ 5, 6, 7, 8 },
						{ 9, 10, 11, 12 } };
		print2D(mat);
	}
}

Method 4 (Prints in matrix style Using Arrays.deepToString())

Arrays.deepToString(int[][]) converts  2D array to string in a single step.

// Java program to print the elements of
// a 2 D array or matrix using deepToString()
import java.io.*;
import java.util.*;
class GFG {

	public static void print2D(int mat[][])
	{
		System.out.println(Arrays.deepToString(mat));
	}

	public static void main(String args[])
		throws IOException
	{
		int mat[][] = { { 1, 2, 3, 4 },
						{ 5, 6, 7, 8 },
						{ 9, 10, 11, 12 } };
		print2D(mat);
	}
}