The Java virtual machine allocates these 26 arrays on the heap, initializes their components such that they form a tree, and returns the reference to the base array. In response to the multianewarray instruction in the initAnArray() method, the Java virtual machine creates one five-dimensional array of arrays, five four-dimensional arrays of arrays, and twenty three-dimensional arrays of ints. These components are ints, the elements of this multidimensional array, and theyĪnd they are accessed by threeD through threeD. The components of these five arrays are also references to arrays, each of which has three components. Each component of the base array is itself a reference to a one-dimensional array of four components, accessed by threeD through threeD. In the initAnArray() method, the base array has five components- threeD through threeD. The reference returned by the multianewarray instruction refers to the base one-dimensional array in the tree. In response to the multianewarray instruction, which in this example requests the allocation of a three-dimensional array, the Java virtual machine creates a tree of This simulation demonstrates how the Java virtual machine handles multidimensional arrays. The initAnArray() method merely allocates and initializes a three-dimensional array. Now calculate the int that will be assignedĢ9 iload_1 // Push int from local variable 1 (i).ģ0 iload_2 // Push int from local variable 2 (j).ģ1 iadd // Pop two ints, add them, push int result (i + j).ģ2 iload_3 // Push int from local variable 3 (k).ģ3 iadd // Pop two ints, add them, push intģ4 iastore // Pop value, index, and arrayref assignģ5 iinc 3 1 // Increment by 1 the int in local variable 3: ++k ģ8 iload_3 // Push int from local variable 3 (k).Ĥ0 if_icmplt 23 // Pop right and left ints, jump if left < right:Ĥ3 iinc 2 1 // Increment by 1 the int in local variable 2: ++j Ĥ6 iload_2 // Push int from local variable 2 (j).Ĥ8 if_icmplt 18 // Pop right and left ints, jump if left < right:ĥ1 iinc 1 1 // Increment by 1 the int in local variable 1: ++i ĥ4 iload_1 // Push int from local variable 1 (i).ĥ6 if_icmplt 13 // Pop right and left ints, jump if left < right: at arrayref (gets threeD).Ģ8 iload_3 // Push int from local variable 3 (k). constant pool entry #2 as the class (whichħ astore_0 // Pop object ref into local variable 0:ĩ istore_1 // Pop int into local variable 1: int i = 0 ġ0 goto 54 // Go to section of code that tests outer loop.ġ4 istore_2 // Pop int into local variable 2: int j = 0 ġ5 goto 46 // Go to section of code that tests middle loop.ġ9 istore_3 // Pop int into local variable 3: int k = 0 Ģ0 goto 38 // Go to section of code that tests inner loop.Ģ3 aload_0 // Push object ref from local variable 0.Ģ4 iload_1 // Push int from local variable 1 (i).Ģ5 aaload // Pop index and arrayref, push object refĢ6 iload_2 // Push int from local variable 2 (j).Ģ7 aaload // Pop index and arrayref, push object ref Create a new multi-dimensional array using The bytecodes generated by javac for initAnArray() are shown below: On CD-ROM in file opcodes/ex1/ThreeDTree.java The bytecode sequence in the simulation was generated by javac for the initAnArray() method of the class shown below: This applet accompanies Chapter 15, 'Objects and Arrays,' of Inside the Java 2 Virtual Machine.įor some reason, your browser won't let you view this way cool Java applet. Let newArrLength = arr.The Three-Dimensional Array applet, included below, demonstrates a Java virtual machine executing a sequence of bytecodes. If applied on an empty array, the return value is undefined (obviously, because the array doesn’t even have any value in the first place) Example let array1 =

The method has a return value which is the element it pops out (removes). When it is applied to an array, the length of the array changes – reduces by 1.

i.e it removes the element at the highest index value – array.

The pop() method is a method applied on arrays which removes the last element of the array.

Java array pop