Infix to Postfix Conversion

Following is the java code for converting from infix to postfix:

// To convert Infix into Postfix import java.io.*; class infix2 { public static void main(String args[]) throws IOException { check obj=new check(); String str = new String(); char infix[]=new char[15]; char postfix[]=new char[15]; char stack[]=new char[15]; int len=0,i=0,j=0,top=-1,value; BufferedReader b=new BufferedReader(new InputStreamReader(System.in)); System.out.println("Enter Expression ==> "); str=b.readLine(); len=str.length(); infix=str.toCharArray(); for(i=0;i<=len-1;i++) { int t=obj.isoperand(infix[i]); if(t==1) { postfix[j]=infix[i]; j++; } else if(top==-1) { top++; stack[top]=infix[i]; } else if(infix[i]==')') { while(stack[top]!='(') { postfix[j]=stack[top]; top--; j++; } top--; } else if(obj.priority(infix[i])>obj.priority(stack[top])) { top++; stack[top]=infix[i]; } else { if(obj.priority(infix[i])==obj.priority(stack[top])) { postfix[j]=stack[top]; top--; j++; } else { while(obj.priority(infix[i])<obj.priority(stack[top]) && top!=-1 && stack[top]!='(') { postfix[j]=stack[top]; top--; j++; } } top++; stack[top]=infix[i]; } } //end of for loop while(top!=-1) { postfix[j]=stack[top]; top--; j++; } System.out.println("The Postfix Expression is"); for(i=0;i<len;i++) System.out.print(postfix[i]); }//end of main }//end of class class check { int isoperand(char ch) { if((ch>='A' && ch<='Z' )|| (ch>='a' && ch<='z')) return 1; else return 0; }//end of isoperand method int priority(char ch) { if(ch=='(') return 4; if(ch=='^' || ch=='%') return 3; if(ch=='*' || ch=='/') return 2; if(ch=='+' || ch=='-') return 1; if(ch==')') return 0; return -1; }//end of priority method }//end of class check

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