View Compilation Error

0_0_2931130_5471\Main.java:1: 需要 <标识符>
import java.math.;
                 ^
0_0_2931130_5471\Main.java:2: 需要 <标识符>
import java.io.;
               ^
0_0_2931130_5471\Main.java:3: 需要 <标识符>
import java.util.;
                 ^
0_0_2931130_5471\Main.java:25: 空字符字面值
        	if(ch.charAt(0)==''ch.charAt(0)=='+'n%2==0)
        	                 ^
0_0_2931130_5471\Main.java:25: 未结束的字符字面值
        	if(ch.charAt(0)==''ch.charAt(0)=='+'n%2==0)
        	                  ^
0_0_2931130_5471\Main.java:25: 需要 ';'
        	if(ch.charAt(0)==''ch.charAt(0)=='+'n%2==0)
        	                    ^
0_0_2931130_5471\Main.java:25: 非法的表达式开始
        	if(ch.charAt(0)==''ch.charAt(0)=='+'n%2==0)
        	                     ^
0_0_2931130_5471\Main.java:25: 需要 ';'
        	if(ch.charAt(0)==''ch.charAt(0)=='+'n%2==0)
        	                            ^
0_0_2931130_5471\Main.java:25: 不是语句
        	if(ch.charAt(0)==''ch.charAt(0)=='+'n%2==0)
        	                                       ^
0_0_2931130_5471\Main.java:25: 需要 ';'
        	if(ch.charAt(0)==''ch.charAt(0)=='+'n%2==0)
        	                                          ^
0_0_2931130_5471\Main.java:27: "else" 不带有 "if"
        	else 
        	^
0_0_2931130_5471\Main.java:43: 空字符字面值
        		if(ch.charAt(0)==''ch.charAt(0)=='+')
        		                 ^
0_0_2931130_5471\Main.java:43: 未结束的字符字面值
        		if(ch.charAt(0)==''ch.charAt(0)=='+')
        		                  ^
0_0_2931130_5471\Main.java:43: 需要 ';'
        		if(ch.charAt(0)==''ch.charAt(0)=='+')
        		                    ^
0_0_2931130_5471\Main.java:43: 非法的表达式开始
        		if(ch.charAt(0)==''ch.charAt(0)=='+')
        		                     ^
0_0_2931130_5471\Main.java:43: 需要 ';'
        		if(ch.charAt(0)==''ch.charAt(0)=='+')
        		                            ^
0_0_2931130_5471\Main.java:61: "else" 不带有 "if"
        		else
        		^
0_0_2931130_5471\Main.java:79: 空字符字面值
            		else if(last_sign=='')
            		                   ^
0_0_2931130_5471\Main.java:79: 未结束的字符字面值
            		else if(last_sign=='')
            		                    ^
0_0_2931130_5471\Main.java:79: 需要 ';'
            		else if(last_sign=='')
            		                      ^
0_0_2931130_5471\Main.java:90: 需要 ')'
        	else System.out.println(Invalid Expression!);
        	                               ^
0_0_2931130_5471\Main.java:90: 非法的表达式开始
        	else System.out.println(Invalid Expression!);
        	                                           ^
0_0_2931130_5471\Main.java:90: 不是语句
        	else System.out.println(Invalid Expression!);
        	                                          ^
0_0_2931130_5471\Main.java:93: 需要为 class、interface 或 enum
}