public class Test {

    public static void main(String[] args) {
        int[] a = {3,4,5,6};
        int[] b = {3,4,7,8};      
        
        
        for (int i=0; i<b.length; i++) {
            Boolean flag=false;
          for(int j=0;j<a.length;j++){
              if(b[i]==a[j]){
                  flag=true;
              }              
          }
            if(flag==false){
                System.out.println(b[i]);
            }
           }
        
    }


}

------解决方案--------------------
Java code

        int[] a = {3,4,5,6};
        int[] b = {3,4,6,7,8,9,1,2,5};
        int j;
        for (int i=0; i<b.length; i++) {
            for (j=0; j<a.length; j++) 
                if (a[j]==b[i]) break;
            if (j==a.length) System.out.println(b[i]);
        }