Calculator solving three digits doesn't work properly

So my calculator works perfectly with any calculations involving two digits including the C button however if i attempt any three digits calculations this doesnt really work for example 1 + 2 + 3 = 5 could someone tell me why is that and anyway i could fix it?

public class Calculator {  

  private long currentInput;          //current input
  private long previousInput;         // previous input
  private long result;            // result of calculation
  private String lastOperator = "";  // keeps track of the last operator entered


  /* New digit entered as integer value i - moves currentInput 1 decimal place to the left and adds i in "one's column" */
  public void inDigit(long i) {
    currentInput = (currentInput * 10) + i;
  }


  /* Operator entered  + - or *   */
  public void inOperator(String op) {
    previousInput = currentInput;      // save the new input as previous to get ready for next input
    currentInput = 0;
    lastOperator = op;                 // remember which operator was entered
  } 


   /* Equals operation sets result to previousInput + - 开发者_高级运维or * currentInput (depending on lastOperator) */
  public void inEquals() {
    if (lastOperator.equals("+")) {
      result = previousInput + currentInput;
    } else if (lastOperator.equals("-")) { 
      result = previousInput - currentInput;
    } else if (lastOperator.equals("*"))  {
      result = previousInput * currentInput;
    } 
    lastOperator = "";       // reset last operator to "nothing"
  }


  /* Clear operation */
  public void inClear() {
    currentInput = 0;
    previousInput = 0;
    result = 0;
    lastOperator = "";
  } 

  /* returns the current result */
  public String getResult() {  
    return Long.toString(result);  //converts int to String
  }

  /* returns the previous input value */
  public String getPreviousInput() {
    return Long.toString(previousInput);
  }
  /* returns the current input value */
  public String getCurrentInput() {
    return Long.toString(currentInput);
  }

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Well, you're only storing the last two operands, so for your example of 1 + 2 + 3 = 5, the 1 is lost when you enter the second + sign, and 2 + 3 = 5.

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You only store the last two "inputs" entered (in previousInput and currentInput) so when you go to three or more operands without first hitting =, all but the most recent two disappear.

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your problem is when you add a new operator you just shift your values with out doing any calculations, if a previous operator is stored and both values are set when adding a new operator you need to do calculations for the existing values and operator before changing the stored operator

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Because in your InEquals() method, you only use previousInput and currentInput so your 1 + 2 + 3 = 5 because for the 2nd '+' result = 2 + 3